Changes "silently" fail when boot partition is read-only

[haukex]

Steps to reproduce:

1. Connect via SSH
2. sudo raspi-config
3. Performance Options -> Overlay File System
4. "Would you like the overlay file system to be enabled?" -> No
5. "Would you like the boot partition to be write-protected?" -> Yes
6. Finish, "Would you like to reboot now?" -> Yes (immediate disconnect)
7. Reconnect, sudo raspi-config
8. for example: Interface Options -> Serial Port and make changes
9. Finish, "Would you like to reboot now?" -> Yes (immediate disconnect)

Problem: The changes made to (for example) the serial port configuration haven't actually been made.

The following error messages are only shown if selecting "Would you like to reboot now?" -> No, but when selecting "Yes", these messages may never be shown to the user due to the immediate reboot+disconnect, meaning it appears to the user that the changes have been made.

sed: couldn't open temporary file /boot/firmware/sed5eiXAv: Read-only file system
/usr/bin/raspi-config: 338: cannot create /boot/firmware/config.txt.bak: Read-only file system
mv: cannot stat '/boot/firmware/config.txt.bak': No such file or directory

Suggestion: I think it would be good if either raspi-config were to check for an overlay filesystem and read-only boot partition when starting and warn the user that changes may not be persisted, and/or if the above errors were fatal and/or shown in a dialog box (especially before rebooting).

How open are you to pull requests? I could perhaps implement a warning dialog if the overlay filesystem and/or read-only boot partition are enabled.