[clangd] Rename constructors and destructors in cross-file case

* Use ad-hoc Decl canonicalization from Clang-Rename to allow renaming
  constructors and destructors while using cross-file rename.
* Manually handle the destructor selection
* Add unit tests to prevent regressions and ensure the correct behaviour

Reviewed by: sammccall

Differential Revision: https://reviews.llvm.org/D71247