…k-Simulacrum

compiletest: don't use `std::io::stdout()`, as it bypasses `set_print`.

This PR undoes a change made during rust-lang#69916, which became unnecessary during review but was left in by accident, and which isn't correct due to `libtest` using `std::io::set_print`, which overwrites the `println!` behavior but *not* `writeln!(std::io::stdout(), ...)`.

The effect of using `writeln!(std::io::stdout(), ...)` was that the diff output would show *while* running the tests, instead of at the end, when failing tests are listed.

r? @Mark-Simulacrum cc @oli-obk

Rollup of 6 pull requests

Successful merges:

 - rust-lang#70535 (Track the finalizing node in the specialization graph)
 - rust-lang#70590 (Miri: make backtrace function names and spans match up)
 - rust-lang#70616 (rustc_target::abi: rename FieldPlacement to FieldsShape.)
 - rust-lang#70626 (cargotest: remove webrender)
 - rust-lang#70649 (clean up E0468 explanation)
 - rust-lang#70662 (compiletest: don't use `std::io::stdout()`, as it bypasses `set_print`.)

Failed merges:

r? @ghost