[Improvement] Point DW tests to a datawarehouse instead of an mssql db.

Currently with this pr: https://github.com/Azure/data-api-builder/pull/1877, we have a seperate pipeline for DW integration tests. However, it provisions a mssql db underneath and executes the queries against it. This issue tracks changing this to execute against a datawarehouse. Some clarity is needed on how to provision a data warehouse on azure pipeline to do this sort of testing.