Split DescribeAddressIfShadow between a function that gets all the...

Split DescribeAddressIfShadow between a function that gets all the information, and one that prints it.

Summary:
Replacement for part of D23518
This is the first patch to start reifying information about errors. It deals only with reifying shadow address-related information.
It will allow us to generate structures with all the relevant information for a given error so a debugger can get to them or they can be included in a core dump.

Reviewers: kcc, samsonov

Subscribers: kubabrecka, llvm-commits

Differential Revision: https://reviews.llvm.org/D23519

llvm-svn: 278718