- Add integration test for serving cert auto-generation and rotation
- Add unit test for `WithInitialEvent` of the cert manager controller
- Move UpdateAPIService() into the `apicerts` package, since that is
the only user of the function.
- Add a unit test for each cert controller
- Make DynamicTLSServingCertProvider an interface and use a mutex
internally
- Create a shared ToPEM function instead of having two very similar
functions
- Move the ObservableWithInformerOption test helper to testutils
- Rename some variables and imports
