review CLI and schema docs

[oliver-sanders]

A lot has changed in Cylc8, we should make a pass through the CLI help to update terminology and make sure nothing has slipped the net.

The Schema docs (used for GraphiQL and the Cylc UI) were largely transferred from the CLI help during earlier Cylc8 development and may have drifted slightly, sometimes purposefully.

Suggest updating the CLI then transferring that across to the Schema. Note that the schema docs are interpreted as markdown.

[oliver-sanders]

#3340

[wxtim]

The CLI docs look OK to me. Are there any particular examples you'd spotted?

I'm not sure that I understand where I'm looking for the schema docs...

[wxtim]

This should have been closed by #4473