[AST] Traverse the class type loc inside the member type loc.

Summary:
We are missing this currently.

This would fix https://github.com/clangd/clangd/issues/216.

Reviewers: ilya-biryukov

Subscribers: mgorny, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70849