Implement a "play task" button in the backend task list view

[bembelimen]

Describe the solution you'd like

The admin should be able to run (published and unpublished) tasks directly from the backend by clicking a button in the list view of the scheduler component.

• [x] Implemented a test run permission on task level
• [x] Implemented a plugin entry point
• [x] Extend the list view to show a play button
• [x] Output the result in an info box

[ditsuke]

Closed by #33