Auto merge of #145284 - nnethercote:type_name-print-regions, r=lcnr

Print regions in `type_name`.

Currently they are skipped, which is a bit weird, and it sometimes causes malformed output like `Foo<>` and `dyn Bar<, A = u32>`.

Most regions are erased by the time `type_name` does its work. So all regions are now printed as `'_` in non-optional places. Not perfect, but better than the status quo.

`c_name` is updated to trim lifetimes from MIR pass names, so that the `PASS_NAMES` sanity check still works. It is also renamed as `simplify_pass_type_name` and made non-const, because it doesn't need to be const and the non-const implementation is much shorter.

The commit also renames `should_print_region` as `should_print_optional_region`, which makes it clearer that it only applies to some regions.

Fixes rust-lang/rust#145168.

r? `@lcnr`

Author: bors