[Feature] Add start and end time tracking for canary batches

[chethanac15]

Description

This PR implements the feature requested in issue #112 to record the start time and end time for every canary batch in Rollout.

Changes Made

• Added BatchStartTime field to BatchReleaseCanaryStatus in both v1alpha1 and v1beta1
• Added CurrentStepStartTime and CurrentStepEndTime fields to Rollout CanaryStatus
• Implemented timing logic in BatchRelease executor to track batch start times
• Updated Rollout controller to sync timing information from BatchRelease
• Added proper conversion functions for API version compatibility
• Included comprehensive documentation

Benefits

• Users can now track how long each canary batch takes to complete
• Enables better monitoring and alerting based on batch timing
• Helps identify performance issues or bottlenecks in specific batches
• Provides audit trail for deployment timing

Testing

• ✅ Build verification passed
• ✅ Unit tests passed
• ✅ Backward compatibility maintained
• ✅ API validation successful

Related Issue

Fixes #112

Type of Change

• New feature (non-breaking change which adds functionality)
• Documentation update

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[kruise-bot]

Welcome @chethanac15! It looks like this is your first PR to openkruise/rollouts 🎉

[kruise-bot]

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