Document QuerySpec and Criterion

[ndr-brt]

Feature Request

Document QuerySpec and Criterion in the context of management api, with some examples, supported operators list and so on.

Which Areas Would Be Affected?

e.g., DPF, CI, build, transfer, etc.

Why Is the Feature Desired?

Are there any requirements?

Who will sponsor this feature?

Please @-mention the committer that will sponsor your feature.

Solution Proposal

If possible, provide a (brief!) solution proposal.

[ndr-brt]

it's already documented: https://eclipse-edc.github.io/documentation/for-contributors/control-plane/entities/#9-querying-with-queryspec-and-criterion

maybe it could worth move this from "contributors" to "adopters", as it is an hi-level documentation not needed for contribution