[azservicebus] Allow for recreating pagers in the ATOM API

[richardpark-msft]

A pager, which is returned from operations like ListQueues(), should also support serialization. To support this a Pager should also export two fields ('CurrentPageToken' and 'NextPageToken'). These can be retrieved from the pager and stored by the user, and then passed into a function on the AdminClient so a pager can be recreated (this is the serialization/deserialization aspect).

References:

• Pager serialization requirements (as specified here: https://azure.github.io/azure-sdk/golang_introduction.html#golang-pagination-serialization)

[richardpark-msft]

As per @jhendrixMSFT 's comment here (#17915) I don't need to do this. Closing.