[FLINK-17075][coordination] Reconcile deployed Executions

[zentol]

With this PR the JobMaster can detect and reconcile deployments that are missing or unknown.

The TaskExecutor is periodically informing the JobMaster about the set of deployed executions, submitted with the heartbeat.

The Scheduler tracks the set of expected deployments with a new ExecutionDeploymentTracker component. The tracker is updated of deployed/terminated deployments by 2 new listeners in the ExecutionGraph.

The JobMaster reconciles deployments with a new ExecutionDeploymentReconciler component.

If the TaskExecutor is hosting an unexpected execution, then that execution will be canceled.
If the TaskExecutor is unexpectedly not hosting an execution, then the execution is failed in the ExecutionGraph.

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Last check on commit c7057fb (Fri Jul 03 08:18:15 UTC 2020)

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[tillrohrmann]

Thanks for creating this PR @zentol. The changes look already good. I had a couple of minor comments. Please take a look.

[tillrohrmann]

Please also make sure that the failed e2e has not failed because of these changes.

[tillrohrmann]

Thanks for addressing my comments. I had one minor comment. This means the only thing which is left to decide is the interface of the ExecutionDeploymentReconciliationHandler. Concretely whether we want to encourage a call per Execution or also support batched calls.