[vbox-build-flare-vm.py] Handle VM crashes

[Ana06]

Details

I have experienced VM crashes occasionally during FLARE-VM installation (likely due to VM restarts), particularly with newer Debian kernels. The current implementation of vbox-build-flare-vm.py takes snapshots every ~20 minutes, which can be restored in case of a crash. However, this restoration is currently manual. Until the VM is manually restored to a pre-crash snapshot, the script continues to take snapshots of the crashed VM. The script needs to be extended to:

• Detect VM crashes.
• Copy the VirtualBox log to LOGS_DIR for crash debugging.
• Restart a previous snapshot before the crash to resume installation.