Documentation: move dev-tools debugging files to process/debugging/

Documentation: move dev-tools debugging files to process/debugging/

Move gdb and kgdb debugging documentation to the dedicated
debugging directory (Documentation/process/debugging/).
Adjust the index.rst files to follow the file movement.
Adjust files that refer to these moved files to follow the file movement.
Update location of kgdb.rst in MAINTAINERS file.
Add a link from dev-tools/index to process/debugging/index.

Note: translations are not updated.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Sebastian Fricke <sebastian.fricke@collabora.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: workflows@vger.kernel.org
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Daniel Thompson <danielt@kernel.org>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: linux-debuggers@vger.kernel.org
Cc: kgdb-bugreport@lists.sourceforge.net
Cc: Doug Anderson <dianders@chromium.org>
Cc: Alex Shi <alexs@kernel.org>
Cc: Hu Haowen <2023002089@link.tyut.edu.cn>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-serial@vger.kernel.org
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Daniel Thompson <danielt@kernel.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20241210000041.305477-1-rdunlap@infradead.org