[FLINK-21132][runtime] Don't end input on stop with savepoint

[rkhachatryan]

What is the purpose of the change

EndOfInput was used to handle any stopping of the job. When
stopping with savepoint the input is not actually ended.
This causes issues with some sinks (e.g. Iceberg).

With this change, endInput is not call for stop-with-savepoint.

To differentiate stop-with-savepoint from other cases
only checkpoint (RPC/barriers) are considered and not network EOP.
That's enough because EOP is only injected after the CP completion
(i.e. when the downstream is also notified by sync savepoint by CP
barriers).

Verifying this change

• Added SavepointITCase (testStopSavepointWithBoundedInput, testStopSavepointWithBoundedInputConcurrently)
• Added StreamTaskTest (testSyncSavepointAborted,testSyncSavepointAbortedAsync,testSyncSavepointCompleted)

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): yes (endInput is not called anymore for stop-with-savepoint)
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? no

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Automated Checks

Last check on commit 0527a31 (Fri May 28 08:16:57 UTC 2021)

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CI report:

• e313952 UNKNOWN
• 0527a31 Azure: FAILURE

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[rkhachatryan]

CI failure is unrelated (UnalignedCheckpointITCase.execute[Parallel cogroup, p = 10] ).

@flinkbot run azure