Link to test reports from MR Widget

What does this MR do?

This MR adds a button to the MR test report widget that allows the user to go the Test Report tab if enabled.

Change Summary:

• Updated the Test Report component to render the button
• Added the GLFeatures mixin to check if the junitPipelineView feature is enabled
• Changed the merge request controller, so it can record the junitPipelineView key and make it available to the Vue so it can be used for conditional rendering

Tests:

• Wrote a test that checks if the button renders/not renders when junitPipelineView is enabled/disabled
• Created new helper util to mount the component with the provide parameter.

Screenshots

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 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

Resolves #201840 (closed)