[clang] [clang-tools-extra] [clang][Sema] Upstream HeuristicResolver from clangd (PR #121314)

[Nathan Ridge via cfe-commits]

HighCommander4 wrote:

Adding some reviewers. The RFC has been published for a week, and the responses have been favourable with no objections.

https://github.com/llvm/llvm-project/pull/121314