Equinox.Cosmos: Reinstate Tip isa Batch

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The CosmosDb Stored Procedure in 1.x and 2.x guarantees to to never to mutate a document.

This was considered to be a critical guarantee on which internal projection systems would depend.

I'm of the opinion that the At-Least-Once-delivery characteristics of anything consuming from the CosmosDb Change Feed imply any projector can yield repeat sequences that are no different to those one might anticipate were mutation of events taking place.

As a result, the main thing that's necessary to consider exposing this facility is to ensure the following are adhered to:

• Downstreams should not exclude documents with id="-1"
• Downstream projectors should consider removing duplicate events where they are absolutely certain they have already projected an item in the current sessions (as noted above, consumers should already be able to handle partial resends of earlier events, including patterns such as 012314345678129, but this change will certainly make repeats more prevalent(so implementing this may be avoidable))

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Resolves #109

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Superseded by #251