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

[Erich Keane via cfe-commits]

erichkeane wrote:

> I'd like more time to think about this change and discuss it with @AaronBallman / @erichkeane

I'm having some doubts too.  This seems like the sort of thing we usually trace by knowing the original template, and seeing if we aren't that.  So find the thing that owns this expression, and walk over to see if the primary template matches this one (though that isn't a perfect simile here).

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