scan: add a state-totals output format

[oliver-sanders]

Small enhancement requested by Dave for ease of working on awkward platforms without the aid of the GUI.

A one line summary line for cylc scan which includes the state totals (similar to the "rich" format) but without the multiline summary that follows.

Check List

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• Applied any dependency changes to both setup.cfg (and conda-environment.yml if present).
• Tests are included (or explain why tests are not needed).
• CHANGES.md entry included if this is a change that can affect users
• Cylc-Doc pull request opened if required at cylc/cylc-doc/pull/XXXX.
• If this is a bug fix, PR should be raised against the relevant ?.?.x branch.