Port to Azure.Cosmos / v3 SDK

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• Need to figure out best way to invoke stored proc with 3 args, of which one is a large object Most efficient way to call stored proc with >1 arg including a large object Azure/azure-cosmos-dotnet-v3#509
• Need to figure out why 9f94b6d is required (some queries got more expensive) Ported query consuming more RUs in V3 ? Azure/azure-cosmos-dotnet-v3#722
• port eqx dump TODO (deferring for now - V4 port will include it)

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It passes; there's a TODO or two, but in principle this can get merged into master after we declare master to be 3.x-preview-era
(it may make sense to introduce an Equinox.Cosmos2 nuget with identical code using Microsoft.Azure.Documents for backcompat)

[claassistantio]

All committers have signed the CLA.

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Merging to checkpoint this work.

There's in-flight work to migrate Equinox.Cosmos to use the V4 Azure.Cosmos SDK - the likelihood is that there won't thus be a long-lived version of Equinox.Cosmos targettng the V3 client, i.e. the first 3.0.0-beta releases will likely use the V4 SDK