[clang-tools-extra] Add refactoring tool to convert between ternary (?:) expressions and equivalent if/else statements (PR #166822)

[Baranov Victor via cfe-commits]

vbvictor wrote:

> I felt this fits better as a refactoring tool rather than a clang-tidy check, since it’s a structural transformation rather than a diagnostic.

In clang-tidy, we have "modernize" checks whose sole purpose is transform the code. Take a look at https://clang.llvm.org/extra/clang-tidy/checks/modernize/loop-convert.html which transform index-based loops to range-based. 

Anyway, all new top-level tools need to go through RFC process on https://discourse.llvm.org/.

https://github.com/llvm/llvm-project/pull/166822