Feat: Add Cancel Button to Session Detail Page Header

What does this MR do and why?

This MR adds the Cancel button to the page level header and removes it from the existing Session Info Details view.

References

Related GitLab Work Items:

• Work Item: #609573 (closed)
• Task: #618766 (closed)
• Blocked by Chained MR: !251366 (merged)

Screenshots or screen recordings

Before	After	Screen Recording

How to set up and validate locally

For DAP/General Setup

• General DAP: https://docs.gitlab.com/development/duo_agent_platform/
• Assigning Duo to a group: https://docs.gitlab.com/development/ai_features/#run-gitlabduosetup-script
• Make sure you are in SaaS mode with export GITLAB_SIMULATE_SAAS=1 set in your env.runit file in your local gdk.
• Turn on the following feature flags (if necessary): duo_workflow, duo_workflow_in_ci, ai_flow_triggers.

Adding Sessions

1. A: If you see no Sessions, you can trigger one that displays a Pipeline/Job by going to an Issue within your Duo enabled project and clicking the Generate MR with Duo button. It should trigger a new session that you can open up.
2. B: You can also run the following query bundle exec rake "gitlab:duo_workflow:populate[50,20,1,<<YOUR_TEST_GROUP_PATH_HERE>>]" to create new agent sessions. Refresh the page. Make sure the group you are testing in has Duo assigned (see DAP setup above).

Test Session Details (The Actual Testing)

1. Make sure you are in a Duo enabled projects where Sessions permissions have been set.

Test Details Header Cancel State (Page)

1. Trigger a new session. A quick easy way is to tag @duo-developer in a comment/note for Work Items or Merge Requests.
2. Go to the AI > Sessions on the left rail.
3. Click the freshly generated Session.
4. Also, it is good to also have the Side Panel > Sessions tab opened to the session in question. Also open a Session here and click the i at the top to expand the Session Information view.
5. While the Session is in a running state - notice the Cancel button is present.
6. Notice in the Side Panel that the button is no longer shown in the details view.
7. Click the Cancel button on the project page and validate it stops the workflow.

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 #618766 (closed)