OID4VP draft version inconsistencies

[vpilkevych-ddy]

• RFC002 points to OID4VP draft 18 https://github.com/EWC-consortium/eudi-wallet-rfcs/blob/main/ewc-rfc002-present-verifiable-credentials.md#60reference
• RFC100 mentions OID4VP draft 20 https://github.com/EWC-consortium/eudi-wallet-rfcs/blob/main/ewc-rfc100-interoperability-profile-towards-itb-v1.0.md#31-steps-to-conformance
• ITB RFC test suite mentions draft18 multiple times in the test case descriptions despite the fact that some tests require x509* client_id_scheme which has been introduced after the draft 18

👀 @endimion

[endimion]

Thanks for opening this. It is extensively being discussed here : #146

I am adding comments about clienet_id_schemes