Make junit feature flag scoped by project

Part of &3198 (comment 342095957)

What does this MR do?

This MR makes it possible to enable our JUnit feature by project.

By passing the project as a param when checking for feature flag eligibility.

Why are we doing this?

We have some ~performance issues to address in order to remove our junit feature flag which are being working on in this epic.

In the meantime, some users want to enable the feature for specific projects which is not possible today.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team