chore(tls-certificates): migrate the integration tests to Jubilant

[tonyandrewmeyer]

Migrates the tls-certificates interface integration tests from python-libjuju to Jubilant (and pytest-operator to pytest-jubilant).

Initial work done with AI but then manually reviewed by me.

[james-garner-canonical]

WDYT about reducing churn by doing this after the imminent pytest-jubilant 2.0 release?

I also wondered if TLS might prefer to hold off until they migrate their charm integration tests so they're not doing things two different ways at once, but this may not be a real concern.

[tonyandrewmeyer]

WDYT about reducing churn by doing this after the imminent pytest-jubilant 2.0 release?

I can bump it after that. I wonder if there are actually any changes that would break here anyway?

I also wondered if TLS might prefer to hold off until they migrate their charm integration tests so they're not doing things two different ways at once, but this may not be a real concern.

They're welcome to reject the PR or hold off on it, of course. Or, even better, migrate the charm integration tests too - this is partly a demo of how straightforward migration can be (see the transcript linked in the description).

[dimaqq]

I like this.
I think it's an improvement and shows how tests can be migrated.
(still need a TLS review obv.)

[saltiyazan]

Looks good. Thank you for making the change.