Auto merge of #99362 - JohnTitor:rollup-4d5zo9d, r=JohnTitor

Rollup of 7 pull requests

Successful merges:

 - #94927 (Stabilize `let_chains` in Rust 1.64)
 - #97915 (Implement `fmt::Write` for `OsString`)
 - #99036 (Add `#[test]` to functions in test modules)
 - #99088 (Document and stabilize process_set_process_group)
 - #99302 (add tracking issue to generic member access APIs)
 - #99306 (Stabilize `future_poll_fn`)
 - #99354 (Add regression test for #95829)

Failed merges:

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

Author: bors

compiler/rustc_ast/src/lib.rs

@@ -14,7 +14,7 @@
 #![feature(const_trait_impl)]
 #![feature(if_let_guard)]
 #![feature(label_break_value)]
-#![feature(let_chains)]
+#![cfg_attr(bootstrap, feature(let_chains))]
 #![feature(min_specialization)]
 #![feature(negative_impls)]
 #![feature(slice_internals)]

compiler/rustc_ast_lowering/src/lib.rs

@@ -31,7 +31,7 @@
 //! in the HIR, especially for multiple identifiers.
 
 #![feature(box_patterns)]
-#![feature(let_chains)]
+#![cfg_attr(bootstrap, feature(let_chains))]
 #![feature(let_else)]
 #![feature(never_type)]
 #![recursion_limit = "256"]