Rollup of 5 pull requests

Successful merges:

 - rust-lang#124896 (miri: rename intrinsic_fallback_checks_ub to intrinsic_fallback_is_spec)
 - rust-lang#125015 (Pattern types: Prohibit generic args on const params)
 - rust-lang#125049 (Disallow cast with trailing braced macro in let-else)
 - rust-lang#125259 (An async closure may implement `FnMut`/`Fn` if it has no self-borrows)
 - rust-lang#125296 (Fix `unexpected_cfgs` lint on std)

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

Rollup merge of rust-lang#125296 - tesuji:checkcfg-buildstd, r=Nilstrieb,michaelwoerister

Fix `unexpected_cfgs` lint on std

closes rust-lang#125291

r? rust-lang/compiler

… r=bjorn3

Cleanup check-cfg handling in core and std

Follow-up to rust-lang#125296 where we:
 - expect any feature cfg in std, due to `#[path]` imports
 - move some check-cfg args inside the `build.rs` as per Cargo recommendation
 - and replace the fake Cargo feature `"restricted-std"` by the custom cfg `restricted_std`

Fixes rust-lang#125296 (comment)
r? `@bjorn3` (maybe, feel free to re-roll)

Rollup merge of rust-lang#125452 - Urgau:check-cfg-libraries-cleanup, r=bjorn3

Cleanup check-cfg handling in core and std

Follow-up to rust-lang#125296 where we:
 - expect any feature cfg in std, due to `#[path]` imports
 - move some check-cfg args inside the `build.rs` as per Cargo recommendation
 - and replace the fake Cargo feature `"restricted-std"` by the custom cfg `restricted_std`

Fixes rust-lang#125296 (comment)
r? `@bjorn3` (maybe, feel free to re-roll)