Sticky search bar positioning

[neodescis]

Is your feature request related to a problem? Please describe.

Currently when a user is viewing a large dashboard and has to scroll down, the search/filter bar scrolls out of view. To change anything on the search/filter bar, the user has to scroll back up to the top of the dashboard.

Describe the solution you'd like

We would like a toggle setting to be added under the "Appearance" section. If enabled, it would make the search/filter bar "sticky" such that it would stay at the top and not scroll with the dashboard. If turned off (which would be the default), the search bar's positioning would be as it is now.

Describe alternatives you've considered

Haven't thought of any. We are presently deploying a fork of Kibana with this change hard-coded (always-on), but we are moving to Dashboards and would like to add the ability to control it with a settings flag and push the change to the official repository.

Additional context

For us, it is sufficient for this toggle to control the behavior for all of our users, so a global setting is sufficient.