Fix broken JSON-LD contexts (e.g., by inlining)

Several test cases suffer from references to JSON-LD contexts that don't exist. Please fix them, in most cases by inlining the necessary prefix bindings. This will fix the problems discussed at https://gitlab.com/gaia-x/data-infrastructure-federation-services/cat/fc-service/-/issues/69#note_1154463772. @dsukhoroslov FYI.

(General background: We are, via https://gitlab.com/gaia-x/technical-committee/service-characteristics/-/issues/137, on the way towards publishing a standard Gaia-X context in the Gaia-X Registry, but this work is not yet complete.)

I did a quick search over the main branch and found the following problems:

fc-service-core/src/test/resources/Claims-Extraction-Tests/participantSD.jsonld (wants to bind prefixes but gets syntax wrong)
fc-service-core/src/test/resources/Query-Tests/serviceOfferingSD.jsonld (non-existing Gaia-X context)
fc-service-core/src/test/resources/Query-Tests/serviceOfferingSD2.jsonld (non-existing Gaia-X context)
fc-service-core/src/test/resources/Query-Tests/serviceOfferingSD1.jsonld (non-existing Gaia-X context)
fc-service-core/src/test/resources/Query-Tests/serviceOfferingSD3.jsonld (non-existing Gaia-X context)
fc-service-server/src/test/resources/mock-data/new_participant.json (non-existing Gaia-X context)
fc-service-server/src/test/resources/mock-data/participant_without_proofs.json (non-existing Gaia-X context)

There are some more test cases using contexts, but these look valid to me.