Print CGU reuse statistics in `-Zprint-mono-items`

I'm trying to expose more information about incremental profiling from rustc (https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/Profiling.2Fanalysis.20of.20incremental.20builds/with/531383501). One of the things that would be quite useful to expose is the CGU reuse state, so that when you do a rebuild, you can see all the CGUs (and all the functions) that had to be recompiled.

Currently, we have (AFAIK) two ways of outputting monomorphization statistics:
1) `-Zdump-mono-stats` outputs statistics about number of instantiations and expected compilation cost of individual functions in the local crate being compiled. It can be outputted either as Markdown or JSON.
2) `-Zprint-mono-items` outputs a pair (item, CGU) for each monomorphized item.

I was thinking about recording CGU statistics in the self-profile output, but I realized that as a simpler step, we could just add CGU reuse data to `-Zprint-mono-items`, as an additional output. That is what this PR does.

Rollup of 19 pull requests

Successful merges:

 - #144400 (`tests/ui/issues/`: The Issues Strike Back [3/N])
 - #144764 ([codegen] assume the tag, not the relative discriminant)
 - #144807 (Streamline config in bootstrap)
 - #144899 (Print CGU reuse statistics in `-Zprint-mono-items`)
 - #144909 (Add new `test::print_merged_doctests_times` used by rustdoc to display more detailed time information)
 - #144912 (Resolver: introduce a conditionally mutable Resolver for (non-)speculative resolution.)
 - #144914 (Add support for `ty::Instance` path shortening in diagnostics)
 - #144931 ([win][arm64ec] Fix msvc-wholearchive for Arm64EC)
 - #144999 (coverage: Remove all unstable support for MC/DC instrumentation)
 - #145009 (A couple small changes for rust-analyzer next-solver work)
 - #145030 (GVN:  Do not flatten derefs with ProjectionElem::Index. )
 - #145042 (stdarch subtree update)
 - #145047 (move `type_check` out of `compute_regions`)
 - #145051 (Prevent name collisions with internal implementation details)
 - #145053 (Add a lot of NLL `known-bug` tests)
 - #145055 (Move metadata symbol export from exported_non_generic_symbols to exported_symbols)
 - #145057 (Clean up some resolved test regressions of const trait removals in std)
 - #145068 (Readd myself to review queue)
 - #145070 (Add minimal `armv7a-vex-v5` tier three target)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup merge of #144899 - Kobzol:cgu-reuse, r=saethlin

Print CGU reuse statistics in `-Zprint-mono-items`

I'm trying to expose more information about incremental profiling from rustc (https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/Profiling.2Fanalysis.20of.20incremental.20builds/with/531383501). One of the things that would be quite useful to expose is the CGU reuse state, so that when you do a rebuild, you can see all the CGUs (and all the functions) that had to be recompiled.

Currently, we have (AFAIK) two ways of outputting monomorphization statistics:
1) `-Zdump-mono-stats` outputs statistics about number of instantiations and expected compilation cost of individual functions in the local crate being compiled. It can be outputted either as Markdown or JSON.
2) `-Zprint-mono-items` outputs a pair (item, CGU) for each monomorphized item.

I was thinking about recording CGU statistics in the self-profile output, but I realized that as a simpler step, we could just add CGU reuse data to `-Zprint-mono-items`, as an additional output. That is what this PR does.

Rollup of 19 pull requests

Successful merges:

 - rust-lang#144400 (`tests/ui/issues/`: The Issues Strike Back [3/N])
 - rust-lang#144764 ([codegen] assume the tag, not the relative discriminant)
 - rust-lang#144807 (Streamline config in bootstrap)
 - rust-lang#144899 (Print CGU reuse statistics in `-Zprint-mono-items`)
 - rust-lang#144909 (Add new `test::print_merged_doctests_times` used by rustdoc to display more detailed time information)
 - rust-lang#144912 (Resolver: introduce a conditionally mutable Resolver for (non-)speculative resolution.)
 - rust-lang#144914 (Add support for `ty::Instance` path shortening in diagnostics)
 - rust-lang#144931 ([win][arm64ec] Fix msvc-wholearchive for Arm64EC)
 - rust-lang#144999 (coverage: Remove all unstable support for MC/DC instrumentation)
 - rust-lang#145009 (A couple small changes for rust-analyzer next-solver work)
 - rust-lang#145030 (GVN:  Do not flatten derefs with ProjectionElem::Index. )
 - rust-lang#145042 (stdarch subtree update)
 - rust-lang#145047 (move `type_check` out of `compute_regions`)
 - rust-lang#145051 (Prevent name collisions with internal implementation details)
 - rust-lang#145053 (Add a lot of NLL `known-bug` tests)
 - rust-lang#145055 (Move metadata symbol export from exported_non_generic_symbols to exported_symbols)
 - rust-lang#145057 (Clean up some resolved test regressions of const trait removals in std)
 - rust-lang#145068 (Readd myself to review queue)
 - rust-lang#145070 (Add minimal `armv7a-vex-v5` tier three target)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup of 19 pull requests

Successful merges:

 - rust-lang#144400 (`tests/ui/issues/`: The Issues Strike Back [3/N])
 - rust-lang#144764 ([codegen] assume the tag, not the relative discriminant)
 - rust-lang#144807 (Streamline config in bootstrap)
 - rust-lang#144899 (Print CGU reuse statistics in `-Zprint-mono-items`)
 - rust-lang#144909 (Add new `test::print_merged_doctests_times` used by rustdoc to display more detailed time information)
 - rust-lang#144912 (Resolver: introduce a conditionally mutable Resolver for (non-)speculative resolution.)
 - rust-lang#144914 (Add support for `ty::Instance` path shortening in diagnostics)
 - rust-lang#144931 ([win][arm64ec] Fix msvc-wholearchive for Arm64EC)
 - rust-lang#144999 (coverage: Remove all unstable support for MC/DC instrumentation)
 - rust-lang#145009 (A couple small changes for rust-analyzer next-solver work)
 - rust-lang#145030 (GVN:  Do not flatten derefs with ProjectionElem::Index. )
 - rust-lang#145042 (stdarch subtree update)
 - rust-lang#145047 (move `type_check` out of `compute_regions`)
 - rust-lang#145051 (Prevent name collisions with internal implementation details)
 - rust-lang#145053 (Add a lot of NLL `known-bug` tests)
 - rust-lang#145055 (Move metadata symbol export from exported_non_generic_symbols to exported_symbols)
 - rust-lang#145057 (Clean up some resolved test regressions of const trait removals in std)
 - rust-lang#145068 (Readd myself to review queue)
 - rust-lang#145070 (Add minimal `armv7a-vex-v5` tier three target)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup of 19 pull requests

Successful merges:

 - rust-lang#144400 (`tests/ui/issues/`: The Issues Strike Back [3/N])
 - rust-lang#144764 ([codegen] assume the tag, not the relative discriminant)
 - rust-lang#144807 (Streamline config in bootstrap)
 - rust-lang#144899 (Print CGU reuse statistics in `-Zprint-mono-items`)
 - rust-lang#144909 (Add new `test::print_merged_doctests_times` used by rustdoc to display more detailed time information)
 - rust-lang#144912 (Resolver: introduce a conditionally mutable Resolver for (non-)speculative resolution.)
 - rust-lang#144914 (Add support for `ty::Instance` path shortening in diagnostics)
 - rust-lang#144931 ([win][arm64ec] Fix msvc-wholearchive for Arm64EC)
 - rust-lang#144999 (coverage: Remove all unstable support for MC/DC instrumentation)
 - rust-lang#145009 (A couple small changes for rust-analyzer next-solver work)
 - rust-lang#145030 (GVN:  Do not flatten derefs with ProjectionElem::Index. )
 - rust-lang#145042 (stdarch subtree update)
 - rust-lang#145047 (move `type_check` out of `compute_regions`)
 - rust-lang#145051 (Prevent name collisions with internal implementation details)
 - rust-lang#145053 (Add a lot of NLL `known-bug` tests)
 - rust-lang#145055 (Move metadata symbol export from exported_non_generic_symbols to exported_symbols)
 - rust-lang#145057 (Clean up some resolved test regressions of const trait removals in std)
 - rust-lang#145068 (Readd myself to review queue)
 - rust-lang#145070 (Add minimal `armv7a-vex-v5` tier three target)

r? `@ghost`
`@rustbot` modify labels: rollup