Update cosmosdb persistence details

[warwickschroeder]

Update a result of Particular/NServiceBus.Persistence.CosmosDB#896

Update how the container info and partition key is set and retrieved.

Not to be merged until the above PR is released

[jpalac]

Assuming that we would be going with a patch release as we are only fixing bugs, the new version would be 3.1.3, so we need to split up the synthetic key text based on that.

We are also still missing the upgrade guide from v 3.1.2 to 3.1.3.

[warwickschroeder]

Assuming that we would be going with a patch release as we are only fixing bugs, the new version would be 3.1.3, so we need to split up the synthetic key text based on that.

We are also still missing the upgrade guide from v 3.1.2 to 3.1.3.

As discussed, we'll continue with a minor release, not a patch. Ill make the necessary updates and add the upgrade guide.

[jpalac]

Looks good - just a couple of comments.