[FFM-11846] : Store and delete previous version of the FeatureConfig along with the new one in cache

[akiraqb]

[FFM-11846] : Store and delete previous version of the FeatureConfig along with the new one.
 ### What: 
Store and retrieve current and previous version of the feature config.
Delete both versions of the config.
Added tests
 ### Why:
To meet customer's requirements.
 ### Testing:
Locally + unit tests

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[erdirowlands]

This good good. Just one query which may be a non-issue.