[AMDGPU] DWARF proposal changes for expression context
- Clarify what context is used in DWARF expression evaluation.
- Define location descriptions to fully resolve the context and so include the context in their result.
- As a consequence of location descriptions being fully resoved, change address spaces so only a swizzled and unswizzled private address space is defined. The lane is now part of the location description context.
- Clarify how call frame information is used to fully resolve expressions that specify registers.
Reviewed By: scott.linder
Differential Revision: https://reviews.llvm.org/D70523