Refactor pipeline test report store

What does this MR do?

Related to #218725 (closed)

In preparation for using the summary endpoint (which is behind a feature flag), we need to refactor how the store is set up in the test reports component.

Things of note:

• The store is now instantiated in one location and not in every component
• The store is now instantiated with the report endpoints so we don't have to have a setEndpoint action
• The count endpoint is called inside of the store instead of in the bundle file. This helps prepare for the full-fledged summary endpoint which contains the total_count property as well as other information.

This does not require a changelog since it is a refactor and is non-user facing.

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