Implementation for Evaluating Condition and Custom Signals Server Side Remote Config (#824)

* Added implemenation of evaluate function

* Improvement

* Add farmhash to extension whitelist pkg

* Replace farmhash to hashlib

* Added unit testcase

* removed lint error

* add mock test

* resolve lint comments

* Fixed bug

* Added fixes

* Added fixe

* Added fix for lint

* Changed structure of test

* Added fix for comments

* Added fix for comments

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Co-authored-by: Varun Rathore <varunrathore@google.com>

Author: rathovarun1032