feat(retention): introduce flag to force apply retention

[deepgarg-visa]

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)
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[anshbansal]

Here is the schema https://datahubproject.io/docs/generated/metamodel/entities/datahubretention in case you wish to emit a custom retention. Retention is emitted at gms startup. There is no need for this.