[FLINK-13491][datastream] AsyncWaitOperator supports BoundedOneInput

[ifndef-SleePy]

What is the purpose of the change

• AsyncWaitOperator should respect semantics of BoundedOneInput

Brief change log

• AsyncWaitOperator supports BoundedOneInput
• Wait the in-flight inputs in AsyncWaitOperator.endInput
• I keep this waiting operation a bit redundant both in endInput and close because we probably re-think the endInput semantics in the near future
• BTW, I think the resource releasing of AsyncWaitOperator(endInput/close/dispose) is a bit messy. However I would like to discuss it in another thread.

Verifying this change

• This change added tests in AsyncWaitOperatorTest

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, 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? not applicable

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• ❓ 1. The [description] looks good.
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  • Needs attention by @pnowojski [committer]
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CI report:

• ff986e0 : SUCCESS Build

[ifndef-SleePy]

@flinkbot attention @pnowojski

[pnowojski]

LGTM, merging.

Thanks for the fix @ifndef-SleePy