Test: debug.toolbar setting

[isidorn]

Refs: #2513
Complexity: 2

• any os @weinand
• Mac @sandy081

Have a repository that you can debug, for example our smoke test express repo.
Start debugging.

• verify that changing debug.toolbar setting has the expected effect

Set "debug.toolbar": "dock" and

• verify that the inital debug actions are shown as the secondary viewlet actions (under elipses)
• verify that starting two debug sessions is still possible and the session dropdown is not shown (since the user can still change active session using the Call Stack)