gccrs: intrinsics: Cleanup error handling around atomic_store_*

gcc/rust/ChangeLog:

	* backend/rust-compile-intrinsic.cc (check_for_basic_integer_type): New function.
	(build_atomic_builtin_name): Use HIR Type instead of `tree`.
	(atomic_store_handler_inner): Cleanup error handling.
	(unchecked_op_inner): Likewise.

gcc/testsuite/ChangeLog:

	* rust/compile/torture/intrinsics-5.rs: Fix error message.