[clang] [Clang] Introduce a trait to determine the structure binding size (PR #131515)

[Erich Keane via cfe-commits]

erichkeane wrote:

> It looks like this PR introduced some undefined behavior. https://green.lab.llvm.org/job/llvm.org/job/clang-stage2-cmake-RgSan/767/testReport/
> 
> Could you take a look at the failing tests and fix them or revert the PR?

Huh, interesting!  Looks like the APValue wasn't initialized in SOME path but we tried to get it.  Corentin will be in tomorrow morning and will fix it, else I will revert tomorrow. 

https://github.com/llvm/llvm-project/pull/131515