Use the test summary endpoint

What does this MR do?

Related to #218725 (closed)

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

• Moved the dataset to be on the actual test report element
• Changed selectedSuite to be selectedSuiteIndex so that the suite would update after the rest of the report was fetched.
• Changed toggleLoading to setLoading because without the feature flag on multiple requests could be happening and toggle loading at the same time. We need to be able to toggle loading with the summary endpoint feature flag on though. So being specific about what we are setting the loading to is helpful.

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