Disable Enable button for Developers at the Explore level for non-foundational items

What does this MR do and why?

Disable the Enable button for Developers at the Explore level for non-foundational items and consolidate permission helpers.

Changelog: changed

EE: true

References

How to set up and validate locally

1. Log in as developer of project (should not be maintainer of any project)
2. Visit Agents and Flows at Explore level
3. Verify that Enable button is disabled for 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 #604007 (closed)