[hotfix] Fix incorrect messageKey passed in ScalingLimited event

[huyuanfeng2018]

What is the purpose of the change

Fix incorrect messageKey passed in ScalingLimited event. This will cause almost every ScalingLimited event to generate a record, scaling.event.interval will not take effect.

Brief change log

Change the calculation method of messagekey to SCALING_LIMITED + vertex + newParallelism

Verifying this change

Added test in JobVertexScalerTest#testSendingScalingLimitedEvents to test the stability of eventKey when scaleFactor changes do not cause parallelism changes.

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 changes to the CustomResourceDescriptors: (yes / no)
• Core observer or reconciler logic that is regularly executed: (yes / no)

Documentation

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

[gyfora]

Should we add a test to guard against future regression?

[huyuanfeng2018]

Should we add a test to guard against future regression?

Thanks for your quick review, this part of the test has been added