[MVC] Issue to MR - Workflow

Problem

Outlined in &18087

Desired outcome

A first, minimal version that allows us to trigger Duo on an Issue and leads to a Draft MR.

Suggested Solution

1. Create a separate workflow graph, based on software_development but simplified and solely targeted at remote execution
2. The graph automatically:
   1. Uses the issue contents as goal with the clear intent of creating an implementation of the desired changes.
   2. Uses the planner to create a plan
   3. Implements the plan via an execution agent
   4. Commits the changes
   5. Creates an MR at the end with the changes and the plan that was used called out in the MR description.
3. Add a button to the issue view to trigger the graph like we did with Jenkins conversion

out of scope:

• Approving / Modifying the plan: This can be added in a second iteration
• Disambiguation / Clarity judge: This can be added in a third iteration
• Applying changes to the MR, this will get tackled via #508711