Add STOPPED and RESTARTING connector states to testing library

Which use case/requirement will be addressed by the proposed feature?

Background: We use Debezium Docker images to perform integration testing for kcctl. Recently, we added support for stopping (but not deleting) connectors, which was introduced in Kafka Connect 3.5 as part of KIP-875.

Use case: We'd like to use the DebeziumContainer::ensureConnectorState method as part of our tests, but the Connector.State enum doesn't contain the STOPPED state, so currently we have to implement this logic on our own.

Additionally, the RESTARTING state that was added in KIP-745 can cause an IllegalStateException to be thrown from calls to DebeziumContainer::ensureConnectorState and DebeziumContainer::ensureConnectorTaskState if the state for a connector or task is RESTARTING, since that does not correspond to a valid value for the Connector.State enum.

Implementation ideas (optional)

Add the values STOPPED and RESTARTING to the  Connector.State enum.