Auto merge of #149632 - matthiaskrgr:rollup-c5iqgtn, r=matthiaskrgr

Rollup of 10 pull requests

Successful merges:

 - rust-lang/rust#149521 (Improve `io::Error::downcast`)
 - rust-lang/rust#149544 (Only apply `no_mangle_const_items`'s suggestion to plain const items)
 - rust-lang/rust#149545 (fix the check for which expressions read never type)
 - rust-lang/rust#149570 (rename cortex-ar references to unified aarch32)
 - rust-lang/rust#149574 (Batched compiletest Config fixups)
 - rust-lang/rust#149579 (Motor OS: fix compile error)
 - rust-lang/rust#149595 (Tidying up `tests/ui/issues` tests [2/N])
 - rust-lang/rust#149597 (Revert "implement and test `Iterator::{exactly_one, collect_array}`")
 - rust-lang/rust#149608 (Allow PowerPC spe_acc as clobber-only register)
 - rust-lang/rust#149610 (Implement benchmarks for uN::{gather,scatter}_bits)

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

Author: bors