Use the test report summary

What does this MR do?

Related to #218725 (closed)

The test report summary endpoint is behind a feature flag build_report_summary. We can use this endpoint to load the summary of the test report first, and then load the rest of the report when the user clicks on a test suite.

This test_report_summary in the pipeline also allows us to render the total count in the tab without us having to update the badge in JS.

Changelog is not required since the UX difference is behind a feature flag, and the rest of the changes are refactors.

Screenshots

Before - only one request	After - summary request and then full request
test_report_full	test_report_summary

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