[Lens] Allow fields to be dragged from the field list to the dimension flyout

[AlonaNadler]

The new flyout visually makes lens configuration more organized and allows to add more configurations.
When dragging a field to replace existing field Lens doesn't show the highlighting. The highlighting helps understand this is a droppable place

cc: @cchaos

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[flash1293]

Just to make sure - we are talking about this scenario, right?

Hovering over the field input with the e.keyword field does not indicate in any way I can drop it here.

[AlonaNadler]

Yes correct @flash1293

[wylieconlon]

The request is pretty clear. From a technical side we need to verify that the DragDropContext is available this far in the component hierarchy, especially because DragDropContext is owned by the editor frame and not the datasource. The other potential concern is that the droppable styles might interface with the interactivity of the field selector, so we might need some kind of alternative drop target.

[flash1293]

I'm not sure whether this is still a valid request - with #78195 we changed the behavior to closing the flyout if something outside of it is clicked. Because of this it's no longer possible to drag a field from the data panel into the field select in the flyout. @AlonaNadler do you think we should do something else here?

[AlonaNadler]

Playing with master that seem to no longer be a problem. Thanks :)