[Orbit] Add min_delta parameter to NewBestMetric

[LINYV0719]

Description

This PR adds a min_delta parameter to NewBestMetric. Motivation: In many training scenarios, we want to avoid saving checkpoints or triggering actions for negligible improvements (e.g., floating point noise). min_delta allows users to specify a minimum threshold for improvement. Changes:

Added min_delta to NewBestMetric.init.

Updated test() logic to require new_value > best_value + min_delta (if higher is better).

Added unit test test_new_best_metric_with_min_delta in new_best_metric_test.py.

Type of change

For a new feature or function, please create an issue first to discuss it with us before submitting a pull request.

Note: Please delete options that are not relevant.

• [x] New feature (non-breaking change which adds functionality)

Tests

I added a new test case test_new_best_metric_with_min_delta in orbit/actions/new_best_metric_test.py to verify the new functionality.

Test Configuration:

• OS: Windows 11
• Python Version: 3.10
• Command: python -m orbit.actions.new_best_metric_test
• Result: Passed

Checklist

• [x] I have signed the Contributor License Agreement.
• [x] I have read guidelines for pull request.
• [x] My code follows the coding guidelines.
• [x] I have performed a self code review of my own code.
• [x] I have commented my code, particularly in hard-to-understand areas.
• [x] I have made corresponding changes to the documentation.
• [x] My changes generate no new warnings.
• [x] I have added tests that prove my fix is effective or that my feature works.