[clangd] Implement range patching heuristics for cross-file rename.

Reviewers: sammccall, ilya-biryukov

Reviewed By: sammccall

Subscribers: merge_guards_bot, MaskRay, jkorous, mgrang, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70594