## Description
This PR fixes an oversight in the implementation of the resolvers of different backends. To implement resolution from environment variables, both MSSQL and BigQuery were directly fetching the process' environment variables, instead of using the careful curated set we thread from main. It was working just fine on OSS, but is failing on Cloud.
This PR fixes this by adding an additional argument to `resolveSourceConfig`, to ensure that backends always use the correct set of variables.
https://github.com/hasura/graphql-engine-mono/pull/1891
GitOrigin-RevId: 58644cab7d041a8bf4235e2acfe9cf71533a92a1
