Rollup merge of #136439 - yotamofek:pr/codegen-ssa-no-indexing, r=Noratrieb

Misc. `rustc_codegen_ssa` cleanups 🧹

Just a bunch of stuff I found while reading the crate's code.
Each commit can stand on its own.
Maybe r? `@Noratrieb` because I saw you did some similar cleanups on these files a while ago? (feel free to re-assign, I'm just guessing)

Author: tgross35