[FLINK-36090][Runtime / State Backends] Fix bug with IngestDB restore operation for priority queue state in backend.

[max-509]

What is the purpose of the change

This pull request fix IngestDB restore operation correctness with priority queue states.

Brief change log

• equals() and hashCode was added to RegisteredPriorityQueueStateBackendMetaInfo

Verifying this change

This change is a trivial rework.

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:

• 91a0968b0e7d74df2a503ee772c37bd386b5e649 Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

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

[mayuehappy]

@max-509 Thanks for reporting this issue ! This fix is LGTM. @StefanRRichter Can you take another review ?

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