[clang] [clang-tools-extra] [clang][CodeComplete] Use HeuristicResolver to resolve pointee types (PR #121315)

[Nathan Ridge via cfe-commits]

HighCommander4 wrote:

Rebased on top of #123549. (I forgot to set up the stacking properly, so the commits from #123549 show up here too. They will go away after #123549 merges and I rebase again.)

Confirmed locally that `Clang.Index/complete-memfunc-cvquals.cpp` is now passing.

https://github.com/llvm/llvm-project/pull/121315