User preferences should have the ability to be configured in ways other than manually

## What?

As a graylog user, if I have large amounts of users I need to configure the preferences manually. A better method would be to either assign roles/permissions to do this or do this programmatically via API (or even disable modifying preferences all together).

## Why?

When there are lots of users this can take a long time or in the event there are expensive queries due to autocompletion, this makes the cluster unstable. If we turn off auto-completion for example, there is nothing stopping a user from turning it back on.

This is tied to HS - 2287918226