Chore: Change sessions filter token helper to use filtered_search_utils

What does this MR do and why?

Originally:

This MR moves the filter token helper for Sessions into into the utils file. Also, since we have a utils folder - moving utils.js into the directory as index.js.

Moved to:

Moved to using the filtered_search_utils and keeping things within the file.

References

• Related GitLab Work Item: #628798 (closed)

Screenshots or screen recordings

No UI changes were made

How to set up and validate locally

Setup + Notes

For sanity, will need to regression test just to make sure the Search functionality still acts the same. Please follow the following steps.

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).

Testing (the Actual Testing)

1. Go to your Project Sessions pages, AI > Sessions.
2. Use the filters for the search, see that it behaves as expected.
3. Go to your Side Panel Sessions (on the right).
4. Repeat Step 2.

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 #628798 (closed)