[clang] [clang] Fix CTAD not respect default template arguments that were added after the definition. (PR #75569)

[Shafik Yaghmour via cfe-commits]

shafik wrote:

Can we please add more detailed summaries, we want the git log to be sufficient for triaging various issues without having to dig into each commit individually.

https://github.com/llvm/llvm-project/pull/75569