[compiler-rt] [sanitizer_common] Tighten operator new allocator nullptr contract (PR #225895)

[Justin T. Gibbs via llvm-commits]

scsiguy wrote:

> > Depends on #225847
> 
> This does not look like a proper stack, I expected to see only diff from 225847.
> 
> But I don't mind if you merge 225847 and 225895 together and even expand on all sanitizers

I've combined this into #225847, and fixed up the other sanitizers there.

https://github.com/llvm/llvm-project/pull/225895