[clang] [clang-tools-extra] [clang-tidy] Add new check: `readability-redundant-typename` (PR #161574)

[Victor Chernyakin via cfe-commits]

localspook wrote:

Gentle ping. Since this is a new check, it would be especially good to get a second review.

(Ignore the close and reopen. I messed up my git push so badly that GitHub closed the PR, whoops...)

https://github.com/llvm/llvm-project/pull/161574