Proof request attribute value restrictions should only be allowed for values that are exposed

[TimoGlastra]

It should not be possible to use query restrictions in an anoncreds proof request without revealing those attributes.

I.e. A proof request with attr::age::value should not be allowed if there's no requested attribute with that. Markers should be allowed maybe, as they're less revealing. But they have become basically obsolete with credentials not supporting optionality anymore (hyperledger/anoncreds-rs#290).

This has a security impact as you can filter credentials without the values being exposed. It doesn't give you a guarantee but can result in knowing what other fields are in the credential.