Make IRBuilder automatically set alignment on load/store/alloca.

This is equivalent in terms of LLVM IR semantics, but we want to
transition away from using MaybeAlign to represent the alignment of
these instructions.

Differential Revision: https://reviews.llvm.org/D77984

GitOrigin-RevId: 89e0662dee5fa541f284e6be0af9e36e7f39f947
4 files changed