Add "changed in version x.y.z" notes to config descriptions

[MetRonnie]

cylc-sphinx-extensions provides prominent versionchanged labels which would be nice to use in the workflow and global config docs, in order to bring attention to changes.

https://cylc.github.io/cylc-sphinx-extensions/extensions/cylc.sphinx_ext.rtd_theme_addons.html#module-cylc.sphinx_ext.rtd_theme_addons

Pull requests welcome!

[oliver-sanders]

Yes please!

Was going to raise this on the 8.x timeframe, however, it would be good to mark any configurations which have changed between versions 7 and 8 as "changed in version 8.0.0".

[wxtim]

note to self

   .. versionchanged:: 1.2.3

      Something changed!

[wxtim]

This looks fairly horrible to do in practice in terms of trawling through the history. I'm going to make a PR for all the changes I can remember making, especially focusing on Cylc 8 changes. IMO the really important places to put these labels are on changes that are being made from now on.

I think that it might be easier to pass this issue around everyone whose made changes, because it'll be easier do to your own changes.

[MetRonnie]

There is also

.. versionadded:: 8.0.0

which results in

New in version 8.0.0.

[wxtim]

Look at

• Your tickets tagged with config change
• conf: ensure all proposed changes have been enacted #3696

[hjoliver]

Meeting: move to general doc overhaul (Issue "review CLI and schema and stuff") - go through and do the lot at once.

[oliver-sanders]

(I.E. It would be easiest to do this along with #4091)