Sync Selection Scope & Count w/ Presentation & AppUI

[aruniverse]

• the main issue is the selection count in the status bar counting all the elements an assembly is composed of instead of treating the assembly as a single entity when the selection scope is assembly / top assembly
• the underlying cause of this issue is that AppUi 4.x severed its dependencies on Presentation and instead of syncing from the Presentation.selection.selectionChanged it not syncs with the iModel.selectionSet.onChanged which won't consider the selection scope when counting the selection
• solution proposed in the AppUI issue Add SelectionCountField component #323 was to split off a version of that element selection count status bar component that doesn't force it to be synced with the redux store.
• Long term presentation would expose a hook or hoc to wrap that field with to have it easily sync with their selection change event