[OpenMP] Add source location information to the libomptarget profile

In much of the libomptarget interface we have an ident_t object now, if
it is not null we can use it to improve the profile output. For now, we
simply use the ident_t "source information string" as generated by the
FE.

Reviewed By: tianshilei1992

Differential Revision: https://reviews.llvm.org/D95282