[Object Views] Selection of a parent after selecting children not possible in many views

[khalidadil]

Is your feature request related to a problem? Please describe.
For a number of views in Open MCT that contain selectable "sub-objects", once a sub-object is selected there is either no affordance to select the "main" parent object, or an unsatisfactory way to do so via clicking in an "empty" area.

No ability to select parent

Flexible Layouts and Stacked Plots provide absolutely no way to select the parent while in Edit mode. For example, once having selected a single child of a Stacked Plot, like this

it's not possible to select the main parent object and edit its properties without exiting Edit mode and returning.

Select parent by clicking in an "empty" area.

Display Layout, Plan / Gantt and Time Strip views (and, coming soon, Time List views will also have this problem as they will allow a selection on an Activity) all provide a sub-object selection context, but only allow main view parent selection by clicking in an "empty" area of their canvases. But, for very dense views there may actually not be any empty space to click on.

Describe the solution you'd like
We should implement a consistent gesture across all views: It should be possible to click the object name, or in the empty space next to the object name, to return the selection to the parent object. We may also want to consider "toggling" selection, such that clicking a selected child de-selects it and returns the selection context to the main parent object.

[khalidadil]

@charlesh88 Does this issue describe the desired behavior to return to selecting parents that we wanted? We discussed needing a consistent pattern.