VM templates without ssh key overrides network

### Jenkins and plugins versions report

Jenkins 2.462.2
Google Compute Engine Plugin
Version4.575.v6969b_7c435eb_

Im using a VM template, with a non-defaut VPC/network for both nodes, and the server.
The template sets the appropriate network for the node.

This works great if I define the cloud config to use an ssh keypair.
However, if I DONT use that... then apparently the GCE plugin forces the node to be created in the DEFAULT VPC.
Overriding the VM template.

I cant even manually override this myself in the jenkins cloud config side, since all "advanced" settings get ignored if you use a VM template.

### What Operating System are you using (both controller, and any agents involved in the problem)?

ubuntu24

### Reproduction steps

create VM template with non-default VPC

Create jenkins cloud config that uses ssh keypair
Create another cloud config that just uses default gcp creds.

first one works, second one doesnt, if you have security rules in the cloud to disallow crossvpc traffic.

### Expected Results

it would work?

### Actual Results

loop on ssh timeout.
ssh is blocked, and it SHOULD be, because jenksins server is trying to talk to a VM in a different VPC.

### Anything else?

_No response_

### Are you interested in contributing a fix?

_No response_