Store revocation state with the credential record rather than the credential exchange record

[TimoGlastra]

This means you can remove the credentialExchangeRecord and still have the credential data.

In addition, we should start looking at promoting the usage of the credential records itself more over the credential exchange records so that a) you can delete the exchange record but keep the credential and b) works better when we start supporting non-didcomm protocols (such as receiving credentials using openid4vci)

[swcurran]

@ianco — is this in ACA-Py already or should we add the same issue? Thanks.