Rollup merge of #137102 - compiler-errors:name_regions2, r=oli-obk

Rework `name_regions` to not rely on reverse scc graph for non-member-constrain usages

Fixes rust-lang/rust#137015

Splits the `name_regions` into two versions: One meant for member region constraint error reporting (which I've renamed to `name_regions_for_member_constraint`), and one meant *just* to replace region vids with an external region.

Use the latter in the usage sites I added in #136559, since the regions returned by `name_regions_for_member_constraint` are also not *totally* accurate (which is fine for how they're used for member region constraint error reporting -- they're intentionally returning overapproximated universal regions so that we have something to name in `+ use<'a>` suggestions, because opaques can only capture universal regions and since member region constraints don't insert any edges into the region graph, the error region is probably gonna be shorter than a universal region) and because that function requires the reverse scc graph to have been computed which isn't done for our usages in #136559.

Author: matthiaskrgr