Kernel: Allow configuring a Jail to not impose PID isolation restriction

This is quite useful for userspace applications that can't cope with the
restriction, but it's still useful to impose other non-configurable
restrictions by using jails.

Kernel/API/Jail.h

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/EnumBits.h>
+#include <AK/Types.h>
+
+enum class JailIsolationFlags : u32 {
+    None = 0,
+    PIDIsolation = 1 << 0,
+};
+
+AK_ENUM_BITWISE_OPERATORS(JailIsolationFlags);

Kernel/API/Syscall.h

@@ -343,6 +343,7 @@ struct SC_setkeymap_params {
 struct SC_jail_create_params {
     u64 index;
     StringArgument name;
+    int flags;
 };
 
 struct SC_jail_attach_params {