[clang] [Clang] omit parentheses in fold expressions with a single expansion (PR #110761)

[Erich Keane via cfe-commits]

https://github.com/erichkeane requested changes to this pull request.

The test changes are weird, we want to leave all the existing tests in place, because we want this diagnostic to happen.

Also, I'd love it if someone else (@cor3ntin ?) had a think on this as well.

https://github.com/llvm/llvm-project/pull/110761