[FLINK-35047][state] Shutdown StateExecutors when ForStKeyedStateBackend is disposed

[ljz2051]

What is the purpose of the change

This pull request shuts down the ForStStateExecutors when ForStKeyedStateBackend is disposed.

Brief change log

• Shutdown the StateExecutors in ForStKeyedStateBackend.

Verifying this change

This change is already covered by existing tests, such as ForStStateBackendConfigTest and AsyncExecutionControllerTest.

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): no
• 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, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no

[flinkbot]

CI report:

• 1f9e43a60666364085c0567b2a5cdc4e260f4e3e Azure: SUCCESS

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[ljz2051]

I think we'd better note the shutdown contract down into the description/Javadoc of StateExecutor. The StateExecutor is managed by KeyedStateBackend and the AEC or operators won't take care of the lifecycle of it.

@Zakelly Thanks for your suggestion. I have refined the JavaDoc in AsyncKeyedStateBackend#createStateExecutor and StateExecutor.