docs: maintainers_include: split state machine on multiple funcs

docs: maintainers_include: split state machine on multiple funcs

Instead of one big __init__ code, split the MaintainersParser
code in a way that the state machine remains on __init__, but
the actual parser for descriptions and subsystems are moved
to separate functions.

To make parser easier, instead storing parsed results on a list,
place them directly on a string.

That granted 15% of performance increase(*) with Python 3.14 and
made the logic simpler.

(*) measured by creating a new directory under Documentation/,
    and placing justmaintainers.rst and an index file there,
    building it via sphinx-build-wrapper.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Message-ID: <0b72530cf496ce5e2987ca784058a50f4dc814d2.1777987027.git.mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <26376e92a5e31e5d285b8676ed443a247b42e4c5.1778309595.git.mchehab+huawei@kernel.org>