[clang] [clang] Track final substitution for Subst* AST nodes (PR #132748)

[Pranav Kant via cfe-commits]

pranavk wrote:

> @pranavk this test case is fixed by the same fix as for the first mangling issue: https://github.com/llvm/llvm-project/pull/135111

I could still repro this issue after #135111 

https://github.com/llvm/llvm-project/pull/132748