[clangd] Fix hover 'local scope' to include class template params

Summary: Fixes the last part of https://github.com/clangd/clangd/issues/76

Reviewers: kadircet

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

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70325