[FLINK-23003][runtime] Fix resource leak in RocksIncrementalSnapshotStrategy

[fredia]

What is the purpose of the change

This pull request fix resource leak in RocksIncrementalSnapshotStrategy caused by RocksDBStateUploader not being closed.

Brief change log

• Add close() function to RocksDBSnapshotStrategyBase and RocksIncrementalSnapshotStrategy
• Add a call to checkpointSnapshotStrategy.close() in RocksDBKeyedStateBackend#dispose()

Verifying this change

This change can be verified as follows:

• org/apache/flink/contrib/streaming/state/RocksIncrementalCheckpointRescalingTest.java

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

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

Documentation

• Does this pull request introduce a new feature? (yes / no)

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Last check on commit 9c82b0a (Sat Aug 28 12:17:22 UTC 2021)

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CI report:

• 7fd6cd6 UNKNOWN
• 9c82b0a Azure: SUCCESS

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[RocMarshal]

@fredia Thank you for your contribution. LGTM +1, wait the CI passed.

[fredia]

Thank you so much for your review @RocMarshal . Since checkpointSnapshotStrategy is initialized in RocksDBKeyedStateBackendBuilder#build(), but I forgot to close it in the catch statement in RocksDBKeyedStateBackendBuilder#build(), can you re-review it if you got free time?

[rkhachatryan]

Thanks for the fix @fredia, in general LGTM.
I have some minor remarks, PTAL.

Could you please squash the commits and rename it according to
Flink conventions (add jira label, etc.)?

[fredia]

@rkhachatryan Sorry for the irregular naming. I have squashed the commits and renamed them. Can you re-review it if you got free time?

[rkhachatryan]

Thanks for updating your PR @fredia, LGTM.