Ventoy support

There is a new cool open source grub-based loader "Ventoy" designed for creating multi-boot USBs. It can run pure unchanged ISO files. It is possible with some hooks and tricks which make the OS see the ISO content. Ventoy supports Windows and lots of Linux distros but (surprise) has problems with ROS live CD.

There are two boot modes. Default is boot from ISO. But since ROS is not Windows, the windows hook does not apply, so freeldr does not see any files. 

The second mode is map-iso-to-mem then boot (press F1 to enable it). It works, but crashes ROS. 

So, is it possible to fix that? At least the second in-mem mode should work, shouldn't it? If an OS bootloader wishes to support VToy explicitly,  it should read the phy memory address 0x80000~0xA0000 in order to learn, where the boot files are placed:

1. https://ventoy.net/en/doc_compatible_pass.html
2. https://ventoy.net/en/doc_compatible_format.html 

The hardware is VirtualBox 6.1, the SW are both ROS 0.4.14 and nightly 0.4.15-dev-3513-g4ed752e2c56.