[Offload][OMPT][NFCI] Call ompt_libomp_connect instead of dlopen libomp (#214556)

connectLibrary() reached libomp's ompt_libomp_connect through
OmptLibraryConnectorTy, which dlopens "libomp.so" and resolves the
symbol at run time. That cannot do anything the linker has not already
done: libomptarget links libomp and imports seven __kmpc_* symbols from
it, so libomp.so is a DT_NEEDED entry, and libomp defines and exports
ompt_libomp_connect unconditionally -- as a stub in kmp_utility.cpp when
built without OMPT support. Declare it, call it, and delete Connector.h.

AI-assisted.

GitOrigin-RevId: 6824484b6e68ba7f2dff2f63e83f237112f03d9c