Rollup merge of #118268 - compiler-errors:pretty-print, r=estebank

Pretty print `Fn<(..., ...)>` trait refs with parentheses (almost) always

It's almost always better, at least in diagnostics, to print `Fn(i32, u32)` instead of `Fn<(i32, u32)>`.

Related to but doesn't fix #118225. That needs a separate fix.

Author: compiler-errors