Add CLI http comms method

[dwsutherland]

Partially address https://github.com/cylc/cylc-flow/issues/5235 Sibling to https://github.com/cylc/cylc-uiserver/pull/396

Description to come.

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.
• [ ] 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.

[dwsutherland]

We should be able to add the HTTPS comms method to the existing test battery. I've had a crack at the config here but haven't tried it out yet: https://github.com/oliver-sanders/cylc-flow/pull/new/swarm-https

Should we merge that branch into this?

Question:

• Use http or https label?

HTTPS is just the secure version or HTTP but both are still know as HTTP, so given people can use HTTP versions of UIS/hub-proxy, I stuck with http... Or is the point to encourage S use?

[oliver-sanders]

I would label it https just to avoid people thinking it might be unsecured.