Fix cylc lint U013/U015 missing info

[wxtim]

closes #6205

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.

[MetRonnie]

There's a similar issue for

cylc-flow/cylc/flow/scripts/lint.py

Lines 679 to 694 in 75d144e

	'U015': {
	'short': (
	'Deprecated template variables.'),
	'rst': (
	'The following template variables, mostly used in event handlers,'
	'are deprecated, and should be replaced:'
	+ ''.join([
	f'\n * ``{old}`` ⇒ {new}'
	for old, new in DEPRECATED_STRING_TEMPLATES.items()
	])
	),
	'url': (
	'https://cylc.github.io/cylc-doc/stable/html/user-guide/'
	'writing-workflows/runtime.html#task-event-template-variables'
	),
	FUNCTION: check_for_deprecated_task_event_template_vars,

expired handlers = %(suite_uuid)s %(user@host)s

[wxtim]

There's a similar issue for

Re-drafted - I'm going to write an automated test for this.

[wxtim]

This is Separate - I have in my mind that at some point I'm going to refactor out those aspects of Cylc lint which are data rather than infrastructure.

[MetRonnie]

Rather than have to rely on variable names matching here (suggest in this case but vars elsewhere), why not just make the check functions return a list of strings, and add the joined list to the end of the short message?

[wxtim]

Allows us to insert multiple variables

msg = check_meta['short'].format(**check)

It's used by one check.

I've re-drafted this PR - I want to have a think about where I'm going with this....

[wxtim]

Un drafted - I think that my long term goal is to have a better defined check API so that others can add them, but I think I want this fixed sooner, and will worry about that later.

[MetRonnie]

Some minor suggestions