Issuer metadata updates

[dtsiflit]

The following changes introduces to issuer metadata in draft 16:

• Introduce credential_request_encryption
• Add zip_values_supported in credential_response_encryption
• Remove signed_metadata property
• Updates credential_configurations_supported:
  - Values of credential_signing_alg_values_supported are type specific (COSE algorithms used for msoMdoc formated credentials)
  - Property proof_types_supported must be present if cryptographic_binding_methods_supported is present
  - Add credential_metadata property grouping display and claims properties
• Rename ldp_vp to di_vp