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

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

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. 

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