[clang] [Analyzer][CFG] Correctly handle rebuilt default arg and default init expression (PR #117437)

[via cfe-commits]

yronglin wrote:

> I'm WAY happier with this. I don't have the ability to review the SA stuff well enough to give an approval, but the rest of the stuff is good. 1 Nit, else LGTM.

Thanks for the review! There are no functional changes in Static Analyzer after @steakhal's +1 (just renamed a function).

https://github.com/llvm/llvm-project/pull/117437