[OID4VP] VP token validation logic in the Cloud Agent

### Proposed feature

This issue is a subtask of the https://github.com/hyperledger/identus/issues/16

Implement the logic for VP token validation.

### Feature description

The Prover/Wallet submits a VP through the PresentationSubmission Endpoint, so the VP should be validated.

In addition to common VC/VP validation, in OID4VP, additional validations should be enforced, like Authorization Request nonce and aud. See [VP token validation](https://openid.net/specs/openid-4-verifiable-presentations-1_0.html#name-vp-token-validation) for more details.