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

[Carlos Galvez via cfe-commits]

carlosgalvezp wrote:

FYI bisecting https://github.com/llvm/llvm-project/issues/153770 leads to this patch

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