[clang-tools-extra] [clang-tidy] Adds readability-redundant-const check (PR #189733)

[Baranov Victor via cfe-commits]

https://github.com/vbvictor commented:

Can we add test with multiple decls: `constexpr const int a = 1, b = 2` and mixes like `constexpr const int a = 0, &b = a;`. For latter case we can't remove const, but we can give only warning with no fixit.

Did you try to test the check against some codebases (like LLVM). If not, please try to do so to find any FP/FN beforehand.

Otherwise LGTM.

https://github.com/llvm/llvm-project/pull/189733