Prevent Automatic Deletion of Existing VNET By Packer

• We wanted to use our existing VNET which lies in different Resource group, and wanted to make sure it wont get deleted when Packer cleanup its resources.
• Also How can we keep the resources created by packer if we want?

No files or tests are named. Start by tracing the Azure resource cleanup path in packer-plugin-azure and how resources in another Resource Group are tracked. Done should define a way to use an existing VNET without deleting it and an option to retain resources created by Packer.

Written by the indexing model from the issue text.