Remove the dryrun function and use service accounts instead

[scholtzan]

Blocked by #5168

This is the next step after #5168 since this potentially might cause some breakage and different behaviour for users.

We are currently using a Cloud Function for performing dry runs and getting schema information. Ideally, we would like to remove this extra layer of abstraction and just rely on service accounts for doing this.

┆Issue is synchronized with this Jira Task