[FLINK-32079][checkpoint] Support to read/write checkpoint metadata of merged files

[masteryhx]

What is the purpose of the change

Support to read/write checkpoint metadata of merged files

Brief change log

• serialize and deserialize SegmentFileStateHandle in MetadataV2V3SerializerBase
• hotfix error equals for SegmentFileStateHandle

Verifying this change

This change added tests and can be verified as follows:

• Add testSerializeSegmentStateHandle

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, ZooKeeper: (yes / no / don't know)
• The S3 file system connector: (yes / no / don't know)

Documentation

• Does this pull request introduce a new feature? (yes / no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

[flinkbot]

CI report:

• 13447e3 Azure: SUCCESS

Bot commands

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• @flinkbot run azure re-run the last Azure build

[masteryhx]

@Zakelly @fredia Could you take a look ?

[Zakelly]

@Zakelly @fredia Could you take a look ?

@masteryhx
How about waiting for the FLINK-34668, where some new state handles will be introduced.

[masteryhx]

@Zakelly @fredia Could you take a look ?

@masteryhx How about waiting for the FLINK-34668, where some new state handles will be introduced.

Thanks for the suggestion.
I just rework it after rebasing FLINK-34668 .

[Zakelly]

Thanks for this PR! Minor question:

[Zakelly]

IIUC, there is not a chance that EmptySegmentFileStateHandle is serialized here?

[masteryhx]

This serializeStreamStateHandle is used when serialize EmptyFileMergingOperatorStreamStateHandle which holds this as its delegated empty stream state handle.
So it's still needed, right ?

[Zakelly]

Ah.... I missed the serializeStreamStateHandle(stateHandle.getDelegateStateHandle(), dos); part

[Zakelly]

Thanks for the update! LGTM+1