Provisioner `CompleteJob` should do all db operations in a transaction

https://github.com/coder/coder/blob/e6acf821eab1596090e4422419847a3bfd39be6f/coderd/provisionerdserver/provisionerdserver.go#L1259-L1259

Is a 600 line function that does a lot of db mutations. No transaction is used, so partial db mutations can be applied. 

This function should be refactored into smaller functions, and do all it's work in a tx.