As part of the integration testing epic, we should create a type that implements the driver.Deployment interface. Most of the features that need to be tested using mocks are 3.6 and above so this deployment can use just OP_MSG for the time being.

EDIT: Originally, the work for this ticket also involved changing Client to depend on Deployment instead of Topology and adding a NewClientFromDeployment function but that work has been separated off into GODRIVER-1250 instead.