[clang] [UBSAN] add null, alignment and array-bounds checks (PR #190739)

[VASU SHARMA via cfe-commits]

vasu-the-sharma wrote:

> I’m okay with the current changes, except for a few minor nits below. ALso please add a comment explaining why LHS checks are C-only and how this will be covered in a follow up PR as @hubert-reinterpretcast suggested.

Done. Added a comment in the test file for the same.

https://github.com/llvm/llvm-project/pull/190739