Kernel+LibC: Enforce a limit on the number of supplementary group IDs

This patch adds the NGROUPS_MAX constant and enforces it in
sys$setgroups() to ensure that no process has more than 32 supplementary
group IDs.

The number doesn't mean anything in particular, just had to pick a
number. Perhaps one day we'll have a reason to change it.

Kernel/API/POSIX/sys/limits.h

@@ -0,0 +1,9 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#define NGROUPS_MAX 32