feat(ingestion): Add fail-safe stale entity removal via configurable 'fail_safe_threshold' param.

[rslanka]

This PR adds fail-safe mode to the stateful ingestion Stale Entity Removal use-case.

If the percentage of entities that have changed in the current run relative to the previous state is above the configurable fail_safe_threshold, then the fail-safe mode will trigger and

1. the stale entity removal work units won't be emitted corresponding the removed entities in the current run.
2. the latest state won't be committed.

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub

[github-actions]

Unit Test Results (metadata ingestion)

       8 files         8 suites   57m 41s ⏱️
   717 tests    714 ✔️ 3 💤 0 ❌
1 436 runs  1 430 ✔️ 6 💤 0 ❌

Results for commit 9e395d2.

[github-actions]

Unit Test Results (build & test)

562 tests   562 ✔️  13m 32s ⏱️
139 suites      0 💤
139 files        0 ❌

Results for commit 9e395d2.