Support no-external-ip flag in GCE Image Export Tool

[GCE Image Export Tool](https://github.com/GoogleCloudPlatform/compute-image-import/tree/main/cli_tools/gce_vm_image_export) spins up a temporary VM while performing image export. This VM is often created with an external IP address.

I'd like to request that the export tool provides a flag to ensure that the temporary VM is spawn up without a public IP address similar to the `no_external_ip` flag provided in the [import tool](https://github.com/GoogleCloudPlatform/compute-image-import/tree/main/cli_tools/gce_vm_image_import#optional-flags).

Start in cli_tools/gce_vm_image_export and compare its export options with the no_external_ip flag documented for cli_tools/gce_vm_image_import. Trace where the temporary VM is created, then add equivalent flag behavior and verify that exported VMs are created without public IP addresses.

Written by the indexing model from the issue text.