Propagate revocation state of a credential to a target party like "kli vc revoke"

[kentbull]

Feature request description/rationale

There should be functionality in KERIA similar to the kli vc revoke command where a credential issuer can tell a target about the revocation state of a credential.

Specifically, the forwarding.Postman should be used to send the ACDC and all attachments like in kli vc revoke:

class RevokeDoer(doing.DoDoer):
    ...
    def revokeDo(...):
        ....
        self.postman.send(
            src=senderHab.pre, 
            dest=recp, 
            topic="credential", 
            serder=serder,
            attachment=atc)

[kentbull]

As an example use case, this would allow a KERIA agent to present the revocation state of a credential to the Sally component of the vLEI Reporting API just like the command line KLI does.