Add new type of dashboard initial state for the built in and settings based dashboards

Created by: vovakulikov

Context

This PR improves our initial state of empty insights dashboard. Currently, on main we have the following empty dashboard state for all types of dashboards (virtual, built-in like personal and org dashboards, custom type of dashboards that were created by users)

This button create new insight actually makes sense for built-in dashboards (the only one way to add insight to a built-in dashboard is to create a dashboard with some specific to this dashboard visibility settings)

But this create new insight button may confuse users on custom dashboards, cause just to create a code insight isn't enough to see this insight on some custom dashboards. In fact, you have to go to the dashboard page pick the custom dashboard and by dashboard context menu action Add insights add some insight to this custom dashboard.

So I assume it would make sense to have a different initial state for the custom dashboards. This PR add this specific initial state.

By click on add insight, you will see the Add insight to dashboard modal UI

And in this UI you can find and add some insights to the active dashboard.