[asan] Ease dealing with tagged enum ErrorDescription with some macros.

Summary:
Added a macro to enumerate the (error name, error member name) pairs. This way,
when adding an error, we only need to add the pair to one place (plus add its
implementation, or course).

Reviewers: kcc, samsonov

Subscribers: llvm-commits, kubabrecka

Differential Revision: https://reviews.llvm.org/D23875

llvm-svn: 281237