Write integration tests using updated ct-test-srv

[cpu]

This will require refactoring the inclusionChecker, the sctFetcher, and the certSubmitter so that we can call the "work" functions directly without having to interact at the abstraction of the woodpecker like the existing integration tests.

Once refactored we should be able to write small integration tests using the ct-test-srv, switching trees & performing leaf integration on-demand using the management API.