[asan] Store access_size in the {Stack,Global}AddressDescription objects

Summary:
This is important information when we want to describe errors, and should be
part of these descriptions. Otherwise, we need to know the access size when
printing/emitting the description.

Reviewers: kcc, eugenis, vitalybuka

Subscribers: llvm-commits, kubabrecka

Differential Revision: https://reviews.llvm.org/D24387

llvm-svn: 281093