[FLINK-37813][runtime] Pass numberSlots via WorkerRegistration instead of SlotReport

[huwh]

What is the purpose of the change

SlotReport should only report the current slot usage, while numberSlots is an attribute of the TaskManager and should not be included in the SlotReport.

Brief change log

• Pass numberSlots via WorkerRegistration instead of SlotReport

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

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)
• The S3 file system connector: (no)

Documentation

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

[flinkbot]

CI report:

• e52e918 Azure: FAILURE

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[davidradl]

@huwh I am reading the Jira and see the issue was SlotReport of the registered taskmanager did not meet expectations.
I am wondering where it gets the expectations from in the code so I can understand how this change fixes it.

I see the tests add an extra parameter taskExecutorRegistration.getNumberSlots() to ensure they compile. Is there a way to add a unit test that will test the reported scenario for which this fix is addressing.