Fix batching Azure ServiceBus messages to partitioned endpoints #2034
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Fixes #2000.
I don't get the error unless partitioning is enabled on the queue or topic.
There's still a case that's not handled by this PR, and that is if we send messages with different
PartitionKeys in the delivery options. I believe that will need another grouping and handling each partition by itself. I noticed that the PartitionKey does not get mapped byAzureServiceBusEnvelopeMapper, so I didn't attempt to add everything here