Cosmos DB: change feed support (pull model)

[jim-minter]

Feature Request

We would really like to be able to use Cosmos DB's change feed from Go via the official SDK. #18615 is a feature request for providing the entire change feed processor infrastructure in the Go SDK. This feature request is simply to enable the pull model.

I imagine that implementing the pull model in the SDK is a smaller and lower risk lift than implementing the whole change feed processor, and it would be a great step forward. We're fine with manually implementing all of the code around the edges for now rather than using the more opinionated change feed processor model, and we could provide feedback on how we did it which might derisk a future implementation of the change feed processor in a Golang idiom as well.