[clang] [clang-tools-extra] [clang] Improve nested name specifier AST representation (PR #147835)

[Shafik Yaghmour via cfe-commits]

shafik wrote:

Git bisect also blame this PR for: https://github.com/llvm/llvm-project/issues/154270

https://github.com/llvm/llvm-project/pull/147835