[Clang] Add attributes alloc_size and alloc_align to mm_malloc

LLVM optimizes source codes with mm_malloc better, especially due to alignment info.

alloc align https://clang.llvm.org/docs/AttributeReference.html#alloc-align
alloc size https://clang.llvm.org/docs/AttributeReference.html#alloc-size

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D117091