Update the revocation registry definition methods to not generate id based on revocation registry values

[TimoGlastra]

See #4 for general context and possible approaches

As the identifiers can now be any URI, we should update the methods in the AnonCreds library to not generate the id values, but rather allow the user to generate the IDs themselves based on the AnonCreds method they're using.

• Update the credx_create_revocation_registry ffi method based on the chosen approach
  • remove origin_did as parameter
• Update the create_revocation_registry issuer.rs method based on the chosen approach
  • remove origin_did parameter
  • remove the generation of the rev_reg_id based on the input values. The model will now be created without an id property.
• Remove the id property from the revocation registry definition model