[LLD] [COFF] Use the local dwarf code instead of Symbolizer for resolving code locations. NFC.

As we now have code that parses the dwarf info for variable locations,
we can use that instead of relying on the higher level Symbolizer library,
reducing the previous two different dwarf codepaths into one.

Differential Revision: https://reviews.llvm.org/D69198

llvm-svn: 375391