Currently funciton lookup in the expression evaluator
fails to disambiguate member functions the are overloaded
on lvalue/rvalue reference-qualifiers. This happens because
we unconditionally set a `FunctionPrototype`s
`ExtProtoInfo::RefQualifier` to `RQ_None`. We lose
the ref-qualifiers in the synthesized AST and `clang::Sema`
fails to pick a correct overload candidate.
DWARF emits information about a function's ref-qualifiers
in the form of a boolean `DW_AT_rvalue_reference` (for rvalues)
and `DW_AT_reference` (for lvalues).
This patch sets the `FunctionPrototype::ExtProtoInfo::RefQualifier`
based on the DWARF attributes above.
**Testing**
* Added API test
llvm/llvm-project issue #57866
Differential Revision: https://reviews.llvm.org/D134661
