Automatic merge from submit-queue (batch tested with PRs 48497, 48604, 48599, 48560, 48546)

GCE: Use network project id for firewall/route mgmt and zone listing

- Introduces a new environment variable for plumbing the network project id which will be used for firewall and route management. fixes #48515
- onXPN is determined by metadata if config is not specified
- Split `if` conditions: fixes #48521
- Remove `getNetworkNameViaAPICall` which was used as a last resort for the `networkURL` (if empty) which was previously filled with the metadata network project & name.

**Release note**:
```release-note
NONE
```