[clang-tools-extra] [clang-tidy][NFC] Don't qualify names unless strictly necessary (PR #185169)

[Victor Chernyakin via cfe-commits]

localspook wrote:

> Were these changes made using #180404? If not, will be good idea to run new check separately to ensure that it catches same things (except `constexpr` and added namespaces), so it could be used in future to maintain code.

These changes were done semi-manually (mostly using regexes). The check in #180404 deals with a different problem than this PR. The check that *would* deal with this problem is the one requested in the issue linked to by @zwuis

https://github.com/llvm/llvm-project/pull/185169