Enable Premature Cancellation feature for blue/green

[juliev0]

Summary

If user rolls back to the prior version of their Rollout (especially PipelineRollout and MonoVertexRollout), it would be best if they don't have to wait for 5 minutes to start updating back to that version. (This is an ask from the Multiworkload team who will be doing multi-workload automatic rollback.)

Take the scenario of PipelineRollout in a blue/green state:

• pipeline-0: "promoted" and pipeline-1: "upgrading"
• PipelineRollout gets put back to the spec identical to "pipeline-0" before assessment is complete
• We compare the PipelineRollout spec to the "pipeline-0" spec and determine that they are identical. If there is any new update, we can discontinue the in-progress update and start a new one. We perform the same logic we currently do when there is a new PipelineRollout spec after the assessment has been deemed "Failed".

Note: we cannot simply delete the "upgrading" one as one might think. This is because the existing "promoted" one could be on an older version of the isbsvc, and we don't want that. Therefore, we create a new "upgrading" one.

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