…r, r=dtolnay

Use futex-based thread-parker for Wasm32.

This uses the existing `sys_common/thread_parker/futex.rs` futex-based thread parker (that was already used for Linux) for wasm32 as well (if the wasm32 atomics target feature is enabled, which is not the case by default).

Wasm32 provides the basic futex operations as instructions: https://webassembly.github.io/threads/syntax/instructions.html

These are now exposed from `sys::futex::{futex_wait, futex_wake}`, just like on Linux. So, `thread_parker/futex.rs` stays completely unmodified.

…r, r=dtolnay

Use futex-based thread-parker for Wasm32.

This uses the existing `sys_common/thread_parker/futex.rs` futex-based thread parker (that was already used for Linux) for wasm32 as well (if the wasm32 atomics target feature is enabled, which is not the case by default).

Wasm32 provides the basic futex operations as instructions: https://webassembly.github.io/threads/syntax/instructions.html

These are now exposed from `sys::futex::{futex_wait, futex_wake}`, just like on Linux. So, `thread_parker/futex.rs` stays completely unmodified.

Rollup of 14 pull requests

Successful merges:

 - rust-lang#75023 (ensure arguments are included in count mismatch span)
 - rust-lang#75265 (Add `str::{Split,RSplit,SplitN,RSplitN,SplitTerminator,RSplitTerminator,SplitInclusive}::as_str` methods)
 - rust-lang#75675 (mangling: mangle impl params w/ v0 scheme)
 - rust-lang#76084 (Refactor io/buffered.rs into submodules)
 - rust-lang#76119 (Stabilize move_ref_pattern)
 - rust-lang#77493 (ICEs should always print the top of the query stack)
 - rust-lang#77619 (Use futex-based thread-parker for Wasm32.)
 - rust-lang#77646 (For backtrace, use StaticMutex instead of a raw sys Mutex.)
 - rust-lang#77648 (Static mutex is static)
 - rust-lang#77657 (Cleanup cloudabi mutexes and condvars)
 - rust-lang#77672 (Simplify doc-cfg rendering based on the current context)
 - rust-lang#77780 (rustc_parse: fix spans on cast and range exprs with attrs)
 - rust-lang#77935 (BTreeMap: make PartialCmp/PartialEq explicit and tested)
 - rust-lang#77980 (Fix intra doc link for needs_drop)

Failed merges:

r? `@ghost`