Waged pipeline redesign: tests and metrics

[NealSun96]

Issues

• My PR addresses the following Helix issues and references them in the PR description:

Fixes #2287

Description

• Here are some details about my PR, including screenshots of any UI changes:

This adds corresponding metrics and tests for WAGED pipeline redesign.

Tests

• The following tests are written for this issue:

testRebalanceOverwriteTrigger, testEmergencyRebalance

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Changes that Break Backward Compatibility (Optional)

• My PR contains changes that break backward compatibility or previous assumptions for certain methods or API. They include:

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Documentation (Optional)

• In case of new functionality, my PR adds documentation in the following wiki page:

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Commits

• My commits all reference appropriate Apache Helix GitHub issues in their subject lines. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Code Quality

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