Add a frontend feature flag to gate the toggle, connection modal, and awareness callout independently of the backend. Coordinate flag name and rollout plan with PM. Detangle this from the existing mms.featureFlag.atlasSql.clusterSchemaInterface feature flag to only handle the feature enablement/disablement.

Note: I think that we want to go with the new Config Service to take advantage of the extra flexibility to manage feature flag it brings.