Reland "[lldb/DWARF] Only match mangled name in full-name function lookup (with accelerators)"

Summary:

In the spirit of https://reviews.llvm.org/D70846, we only return functions with
matching mangled name from Apple/DebugNamesDWARFIndex::GetFunction if
eFunctionNameTypeFull is requested.

This speeds up lookup in the presence of large amount of class methods of the
same name (a typical examples would be constructors of templates with many
instantiations or overloaded operators).

Reviewers: labath, teemperor

Reviewed By: labath, teemperor

Subscribers: aprantl, arphaman, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D73191