podman: Update VM ssh key

[cfergeau]

podman machine generates a SSH key, and injects it in a generic VM image using ignition.

crc does not use ignition/cloud-init/..., but relies on a hardcoded 'default' key (part of the bundle), and early during the first boot, it replaces it with a newly generated key.

In order to support crc use case we need to either:

1. figure out how to update the SSH key used by podman-machine
2. change snc/crc to use an approach similar to podman's

It's probably easier to go with 1) for now, and to look into 2) as part of the self-sufficient bundle work.

[cfergeau]

1. was done using:

func (d *Driver) UpdateSSHConfig(sshConfig drivers.SSHConfig) error {
	d.vmConfig.Lock()
	defer d.vmConfig.Unlock()
	if err := d.vmConfig.Refresh(); err != nil {
		return fmt.Errorf("reload config: %w", err)
	}
	d.vmConfig.SSH.Port = sshConfig.Port
	d.vmConfig.SSH.IdentityPath = sshConfig.IdentityPath
	d.vmConfig.SSH.RemoteUsername = sshConfig.RemoteUsername
	return d.vmConfig.Write()
}