* hack/{helmfile,helm_vars}: Remove unnecessary hacks

* backend-notification-pusher: Watch RabbitMQ queues to push notifications

Instead of watching brig's federation configs internal endpoint.

* background-notification-pusher: Better function name

* Move federated search tests to new integration suite

The tests require search policy to be set, it is easier to test with dynamic backends.

* Simplify integration tests

Now that allowAll is fixed and is the default for all test backends, we can
write tests in a simpler way.

* background-worker: Do not run federation domains config sync thread

* background-worker: Make remotesRefreshInterval configurable

Defaults to 5 min in the helm chart. For integration tests the value is set to
1s.