Make iPhone tethering work without having to desactivate MAC spoofing in the Welcome Screen

#16180 (closed) added iPhone USB tethering works. However, it requires to disable MAC spoofing, as either the kernel module do not allow it, either the iPhone protocol itself do not allow it, and tails-spoof-mac shutdown the interface if MAC spoofing fails.

As discussed in !77 (merged), for #16987 (closed), this requirement partially reduce the interest of this feature, which can provide a good workaround for when WiFi is not working, but would requires the user to reboot once they discover disabling MAC spoofing is required.

This bug aims to:

• Verify if disabling MAC spoofing is still necessary.
• Propose and implement a workaround.