Add test functionality to EWM integration

What does this MR do and why?

Per #439344 (closed) issue, we're introducing Test settings functionality for IntegrationEWM. By eliminating the testable? method, we are enabling the testing feature for EWM integration at the project level.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Checkout the branch
2. Visit the project's integration page
3. Locate the IntegrationEWM
4. Verify that Test settings button is there! 🎉

Related to #439344 (closed)