Chore: Remove session_details_right_rail feature flag

What does this MR do and why?

This MR removes the session_details_right_rail feature flag from the codebase, but also does a few more things. It also removes the no longer necessary existing agent_flow_info component with it's separate gl-attribute-list as we are now using the new right panel component. It also adjusts the styling of the right panel component to default equal the same widths (290px) as the other right rail components. We're also moving the date/time method into utils.js.

References

• Related GitLab Work Items: #622809 (closed) and #628855 (closed)

Screenshots or screen recordings

Before	After

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.

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 FF Removal

1. Make sure you are in a Duo enabled projects where Sessions permissions have been set.
2. Be sure the following FF cannot be enabled and is not available: session_details_right_rail. You can use the following to toggle it on/off: http://gdk.test:3000/rails/features/

Test FF Removal

1. Make sure the FF has been removed
2. Go to AI > Sessions in the left navigation
3. Select any Session
4. Validate Right Information view displays as expected (make sure the width is the same as in MRs)

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 #622809 (closed)