Leave DW_OP_addr addresses as load addresses in DWARFExpression

DWARFExpression::Evaluate will convert DW_OP_addr addresses in
a DWARF expression into load addresses on the expression stack
when there is a StackFrame in the ExecutionContext, this from
a change in 2018 in https://reviews.llvm.org/D46362.  At the
time this was handling a case that came up in swift programs,
and is no longer necessary.  I generalized this conversion to
a load address when a Target is available in
https://reviews.llvm.org/D137682 to make a test case possible;
this change broke a use case that Ted reported.

This change removes my test case, and removes this conversion
of a DW_OP_addr into a load address in some instances.

Differential Revision: https://reviews.llvm.org/D139226