[clang] [Clang][Parser] Don't always destroy template annotations at the end of a declaration (PR #89494)

[via cfe-commits]

cor3ntin wrote:

My feeling is that it's not worth the complexity.
Getting an accurate benchmak would be difficult, it would only manifest in extremely templated code
I wonder if @AaronBallman has opinion.

https://github.com/llvm/llvm-project/pull/89494