LibJIT: Enable registering JITted objects into GDB

The new JIT::GDB namespace enables registering JITted objects into GDB
dynamically.

Its clients just have to ensure the memory they give to
`register_into_gdb` is in a format that GDB can understand, either by
generating an object file in memory with debug info + symbols or by
registering a custom debug info parser.
None of these are implemented by this API; it only implements the
registering part and lets the client to choose the data format.

GDB JIT Interface:
https://sourceware.org/gdb/current/onlinedocs/gdb.html/JIT-Interface.html#JIT-Interface
Things to take into account from v8's docs, some of which we may
improve: https://v8.dev/docs/gdb-jit#known-limitations

Userland/Libraries/LibJIT/GDB.h

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2023, Jesús Lapastora <cyber.gsuscode@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Span.h>
+
+namespace JIT::GDB {
+
+void register_into_gdb(ReadonlyBytes data);
+void unregister_from_gdb(ReadonlyBytes data);
+}