Consolidate workbench handles of the workbench and the workbench client

[danielwiehl]

Is your feature request related to a problem? Please describe.

A microfrontend can inject a handle to interact with the embedding view or popup. Those handles are slightly different from the normal workbench handles, mainly because they are capability aware. This duplication is especially confusing in the host app because you have to know exactly which handle you are allowed to inject.

Describe the solution you'd like

For the developer, there should be only one WorkbenchView handle and only one WorkbenchPopup handle. Ideally, there would also be only one WorkbenchRouter and one PopupService as well.

Of course, the handles must not know anything about the capability API. Therefore, capability-specific information should be provided via the microfrontend path, e.g. in the form of matrix parameters.