[clang] [UBSAN] add null and alignment checks for aggregates (PR #175032)

[VASU SHARMA via cfe-commits]

vasu-the-sharma wrote:

> > @vasu-the-sharma, can you move this into draft state while we get #175478 and #175023 into shape?
> 
> @vasu-the-sharma, I asked you to move this into draft state. At this point, I think you might want to close this PR and hold off until an internal review of this last PR in the stack determines that it is upstream-ready.

Apologies for the confusion, I forgot to mark this PR as draft. I have closed this PR for now (until the previous one is merged) and will be more careful going forward.

https://github.com/llvm/llvm-project/pull/175032