[clangd] Heuristically resolve dependent call through smart pointer type

Summary: Fixes https://github.com/clangd/clangd/issues/227

Reviewers: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D71644