FQM-323: Verify server prefetch support

[Jammjammjamm]

Summary

This branch adds a check that at least one service advertises prefetch.

Testing Guidance

Test passes against the client suite. Failure is demonstrated in the unit tests.

Anticipated Provider-side Test Impact

None

[arscan]

Is it valid for an instance of a server to not use prefetch in any service because for some reason it just doesn't need them in that case? In which case, I wouldn't call these invalid as implied in the group title "Discovery response contains valid services". I would probably move this out to another simple test that is just "Server demonstrates ability to request the CDS Client perform prefetch queries' (language taken from https://cds-hooks.hl7.org/2026Jan/en/index.html#response). And then in the description note that the tests required demonstration of at least one prefetch query as evidence that it is capable of using prefetch.