Rollup merge of #148194 - Zalathar:no-cleanup, r=jieyouxu

compiletest: Remove `cleanup_debug_info_options`

This "cleanup" function is more than a decade old, and I can't find any evidence of modern-day bootstrap being able to pass any of these flags to `--host-rustcflags` or `--target-rustcflags`.

I thought about replacing the cleanup with an assertion, but I think it's better to delete it entirely for now, and re-add checks later if they're motivated by actual problems in practice.

In addition to deleting some old and confusing code, this also lets us remove three instances of duplicating `TestCx`, which is the biggest win.

r? jieyouxu

Author: matthiaskrgr