Foundational flows using trigger

What does this MR do and why?

This enables foundational flows to be assigned to issues and respectively trigger the flow. Currently we are supporting only assignment trigger and on issues

References

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Pull from !215602 (merged) and !215241 (merged) and restart GDK
2. Follow the steps to create a custom flow and enable in for a project, then create assign trigger for the flow.
3. ::Ai::Catalog::Item.last.update(foundational_flow_reference: 'developer/v1') Update the catalog item to have foundational_flow_reference
4. You should have the service accounts created already.
5. Open any issue for the same project and assign the flow's service account to the issue. You should see a developer/v1 flow started
6. Make sure the flow finishes successfully

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 #582628