Add Cosmos DB integration tests using an emulator

[aslotte]

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Add integration tests similar to SQL Server and SQLite for our Cosmos DB metadata store: https://docs.microsoft.com/en-us/azure/cosmos-db/local-emulator#running-on-docker

[aslotte]

Looking at the documentation, it appears that the current image can only be run in a Window container, which will not work for us (GitHub Actions require them to be able to run in a Linux container)