Resolve "Controller Projects::MergeRequestsController#ci_environments_status.json executes more than 100 SQL queries"

What does this MR do?

This is a first crack at reducing the number of queries in Projects::MergeRequestsController#ci_environments_status.json

It optimizes a small set of queries by caching the service templates query, and only building services when necessary (which caused a query per service).

What are the relevant issue numbers?

Closes #43109 (closed)

Does this MR meet the acceptance criteria?

• [ ] Changelog entry added, if necessary
• [ ] Documentation created/updated
• [ ] Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides