Auto merge of #82999 - cuviper:rustc-rayon-0.3.1, r=Mark-Simulacrum

Update to rustc-rayon 0.3.1

This pulls in rust-lang/rustc-rayon#8 to fix #81425. (h/t `@ammaraskar)`

That revealed weak constraints on `rustc_arena::DropArena`, because its
`DropType` was holding type-erased raw pointers to generic `T`. We can
implement `Send` for `DropType` (under `cfg(parallel_compiler)`) by
requiring all `T: Send` before they're type-erased.

diff --cc Cargo.lock
Simple merge