libgomp: Add OpenMP's omp_target_memset/omp_target_memset_async

libgomp: Add OpenMP's omp_target_memset/omp_target_memset_async

	PR libgomp/120444

include/ChangeLog:

	* cuda/cuda.h (cuMemsetD8, cuMemsetD8Async): Declare.

libgomp/ChangeLog:

	* libgomp-plugin.h (GOMP_OFFLOAD_memset): Declare.
	* libgomp.h (struct gomp_device_descr): Add memset_func.
	* libgomp.map (GOMP_6.0.1): Add omp_target_memset{,_async}.
	* libgomp.texi (Device Memory Routines): Document them.
	* omp.h.in (omp_target_memset, omp_target_memset_async): Declare.
	* omp_lib.f90.in (omp_target_memset, omp_target_memset_async):
	Add interfaces.
	* omp_lib.h.in (omp_target_memset, omp_target_memset_async): Likewise.
	* plugin/cuda-lib.def: Add cuMemsetD8.
	* plugin/plugin-gcn.c (struct hsa_runtime_fn_info): Add
	hsa_amd_memory_fill_fn.
	(init_hsa_runtime_functions): DLSYM_OPT_FN load it.
	(GOMP_OFFLOAD_memset): New.
	* plugin/plugin-nvptx.c (GOMP_OFFLOAD_memset): New.
	* target.c (omp_target_memset_int, omp_target_memset,
	omp_target_memset_async_helper, omp_target_memset_async): New.
	(gomp_load_plugin_for_device): Add DLSYM (memset).
	* testsuite/libgomp.c-c++-common/omp_target_memset.c: New test.
	* testsuite/libgomp.c-c++-common/omp_target_memset-2.c: New test.
	* testsuite/libgomp.c-c++-common/omp_target_memset-3.c: New test.
	* testsuite/libgomp.fortran/omp_target_memset.f90: New test.
	* testsuite/libgomp.fortran/omp_target_memset-2.f90: New test.

(cherry picked from commit 4e47e2f833732c5d9a3c3e69dc753f99b3a56737)