[libc-commits] [libc] [libc] start fix readability-identifier-naming lints (PR #83342)

[Michael Jones via libc-commits]

michaelrj-google wrote:

constexpr should be caps, see: https://github.com/llvm/llvm-project/blob/main/libc/.clang-tidy#L27

https://github.com/llvm/llvm-project/pull/83342