[dsymutil] Fix template stripping in getDIENames(...) to account for overloaded operators

Currently dsymutil when generating accelerator tables will attempt to strip the template parameters from names for subroutines.
For some overload operators which contain < in their names e.g. operator< the current method ends up stripping the operator name as well,
we just end up with the name operator in the table for each case.

Differential Revision: https://reviews.llvm.org/D75545