[Codegen] Emit both AssumeAlignedAttr and AllocAlignAttr assumptions if they exist

Summary:
We shouldn't be just giving up if we find one of them
(like we currently do with `AssumeAlignedAttr`),
we should emit them all.

As the tests show, even if we materialized good knowledge
from `__attribute__((assume_aligned(32)`, it doesn't mean
`__attribute__((alloc_align([...])))` info won't be useful.
It might be, but that isn't given.

Reviewers: erichkeane, jdoerfert, aaron.ballman

Reviewed By: erichkeane

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D72979