Rollup merge of #145474 - fmease:paren-use-bounds-fix, r=fee1-dead

Properly recover from parenthesized use-bounds (precise capturing lists) plus small cleanups

Fixes rust-lang/rust#145470.

First commit fixes the issue, second one performs some desperately needed cleanups.

The fix shouldn't be a breaking change because IINM the parser always ensures that all brackets are balanced (via a buffer of brackets). Meaning even though we used to accept `(use<>` as a valid precise capturing list, it was guaranteed that we would fail in the end.

Author: jieyouxu