Auto merge of #111221 - compiler-errors:yeet-generalizer, r=lcnr

Combine three generalizer implementations

Fixes #111092
Fixes #109505

This code is a bit delicate and there were subtle changes between them, so I'll leave inline comments where further inspection is needed.

Regarding this comment from #109813 -- "add tests triggering all codepaths: at least the combine and the const generalizer", can't really do that now, and I don't really know how we'd get a higher-ranked const error since non-lifetime binders doesn't *really* support `for<const ..>` (it errors out when you try to use it).

r? `@lcnr`

Author: bors