Support inbound Connector restarts

[sbuettner]

Is your feature request related to a problem? Please describe.

There is currently no simple restart mechanism for Inbound Connectors that can be used by developers to restart their Connectors. In case of any client exceptions like networking issues the inbound Connectors are stopping and users have to manually re-deploy their processes to re-activate them.

This is not a great user experience and we can improve this situation with a solution that we already have tested in the Kafka Connector: https://github.com/camunda/connectors/blob/main/connectors/kafka/src/main/java/io/camunda/connector/kafka/inbound/KafkaConnectorConsumer.java#L116

Describe the solution you'd like

We want to simplify the developer experience of handling restarts for inbound connectors and would therefore enhance the existing cancel(final Throwable exception) method implementation.

The cancel method should check the exception and should look for a specific type like for example RestartException. If this exception is thrown the runtime should restart the Connector using the exception properties like backoff time or restart delay.