Auto merge of #117595 - jyn514:x-clippy, r=albertlarsan68

x clippy

thanks to `@asquared31415` `@albertlarsan68` for all their help, most of this pr is their work

note that this also adds x clippy --stage 0 -Awarnings to x86_64-gnu-llvm-15 to make sure it stays working; that won't gate on any clippy warnings, just enforce that clippy doesn't give a hard error. we can't add --stage 1 until clippy fixes its debug assertions not to panic.

note that `x clippy --stage 1` currently breaks when combined with download-rustc.

unlike the previous prs, this doesn't require changes to clippy (it works by using RUSTC_WRAPPER instead), and supports stage 0

read this commit-by-commit

closes rust-lang/rust#107628; see also rust-lang/rust#106394, rust-lang/rust#97443. fixes rust-lang/rust#95988. helps with rust-lang/rust#76495.

r? bootstrap

Author: bors