[Graph] Context menu action to remove all vertices of field

[flash1293]

Currently deselecting a field does not remove the vertices of that field from the workspace. This is confusing in some cases and there is currently no good way to remove all vertices of a given type (e.g. in case this information proved to be irrelevant during an investigation).

By adding a separate item to the field context menu, users can remove all vertices of the given field without breaking the current behavior of removing/adding fields.

In addition to that the color of the vertex should reflect whether a field is currently disabled (by shading the vertex color) to make the state clearer.

[elasticmachine]

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

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[elasticmachine]

Pinging @elastic/kibana-visualizations @elastic/kibana-visualizations-external (Team:Visualizations)

[timductive]

Closing this because it's not planned to be resolved in the foreseeable future. It will be tracked in our Icebox and will be re-opened if our priorities change. Feel free to re-open if you think it should be melted sooner.