Create a FF to disable Zoekt search for SAAS customers

Problem to solve

Sometimes our SaaS customers maybe want to disable Exact code search(Zoekt). Currently its not easily possible for the customers.

Proposal

Create a new FF with the actor namespace. When the FF is enabled for a namespace then the code search should be using Zoekt search, if the FF is disabled for a namespace then the code search should be using Advanced search(Elastic)