Fix trailing slash in reg (workflow name) bug

[MetRonnie]

These changes close #4010

It seems that passing a reg with a trailing slash to the mutations_kwargs dict was the reason for this bug. As such I've fixed it everywhere I found a mutations_kwargs dict.

Does this need a functional test?

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• 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).

• Does not need tests

• Appropriate change log entry included.

• No documentation update required.

• No dependency changes.

[oliver-sanders]

Did you get to the bottom of why the exact argument specified to cylc run mattered?

[oliver-sanders]

I think this is harmless and should work for both REG/path uses, .. in paths now get expanded.

Not so worried about testing as the universal identifier work will centralise this.

[MetRonnie]

Did you get to the bottom of why the exact argument specified to cylc run mattered?

I assumed it's something to do with how mutations are handled, seeing as removing the slash before the mutations_kwargs dict is set is what seems to fix it. (But I have no experience with the mutations stuff)

[hjoliver]

I'm not sure this is the right solution.

If the registered suite name is "foo", then "foo/" is not the correct name, so cylc stop foo/ should say SuiteStopped: foo/ is not running rather than magically convert foo/ to foo. (And vice versa).

If that's confusing because it's easier to accidentally register foo/ than some other wrong character, then we should disallow / at the end of a suite name.

[MetRonnie]

The trouble with that is tab autocompletion adds a trailing slash to the directory name, so it would be an inconvenience to have to remove it every time.

[hjoliver]

OK fair point. Approving on the basis that suite name often mirrors source dir name