Improve certificate management

[rene-dekker]

• Rotate certificates 1 month before expiry (if issued by operator) to minimize potential for down time. (Currently certificates are valid for 825 days.)
• If a certificate is expired, a controller that is fetching a cert for the purpose of adding it to a trusted bundle will skip it. This is similar to the behaviour if a certificate does not exist at all.
• If a certificate is expired, a controller that is responsible for creating it will replace it. (This is already the current behaviour, just mentioning it here for completeness.)
• Improve the test suite, such that cert creation for some certs is done once, and not BeforeEach, cutting down run time of the suite from 40s -> 10s.