Add Duo developer to the flow list

What does this MR do and why?

Changes:

• Add Duo developer to the flow list for the sessions UI
• Moves developer/experimental to duo_developer/v1

References

Relates to #581389 (closed)

DWS MR - gitlab-org/modelops/applied-ml/code-suggestions/ai-assist!4014 (merged)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable FF duo_developer_button
2. Click on Generate MR with Duo button present on issues.
3. Go to the sessions page, you should be able to filter out the flow with name Duo developer

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #581389 (closed)