Enable CI runner in GDK workspace image

Overview

We want to support use cases where team members want to start a workspace with the CI runner enabled, e.g. to test features developed around the related stage.

Impacted categories

The following categories relate to this issue:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Steps to replicate (optional)

Users should be able to create a workspace where GDK is configured to start the CI runner.

@splattael looked into crafting a solution. The current PoC for this is here.