Adding metrics for batched migrations

What does this MR do?

This adds and changes the following metrics:

1. Interval
2. Job duration (instead of efficiency - which is derived)
3. Total tuple count (to derive progress later)

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because not yet released (feature flag).
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content