Preload correct latest test report for requirements

What does this MR do?

Preloads requirements test reports with correct order when using GraphQL lookahead.

Fixes bug where last test report state for a requirement was incorrect because we were not enforcing order on SQL when preloading the association.

Related to #323481 (closed)

Query executed when preloading test reports

SELECT "requirements_management_test_reports".* FROM "requirements_management_test_reports" 
WHERE "requirements_management_test_reports"."requirement_id" IN (12286, 3548, 3547, 6257) 
ORDER BY "requirements_management_test_reports"."created_at" DESC

https://explain.depesz.com/s/jj71

It looks good to me. We could consider adding an index on created_at in the future to support sorting.

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.