Make our USB images work on virtual machines
### GNOME Boxes
Testing with Tails 6.2, I couldn't start GNOME Boxes from an USB image. It silently fails in the UI and outputs the following error message on the command line:
```
(gnome-boxes:47993): Boxes-WARNING **: 12:49:09.329: index-page.vala:181: Failed to create installer media for path '/home/sajolida/iso/tails/tails-amd64-6.2.img': Insufficient metadata on installation media
```
### VirtualBox
We dropped support for VirtualBox in #20241.
It's possible to start VirtualBox from both:
* A physical USB stick, after doing some not-too-complicated magic on the command line:
https://www.how2shout.com/how-to/virtualbox-virtual-machine-boot-usb.html#Step_3_Create_VDMK_Raw_file_of_connected_bootable_USB_drive
Users can use the Persistent Storage on the physical USB stick out of the box.
* A USB image, after converting it to VDI on the command line and increasing its size:
```
$ VBoxManage convertdd eos-eos3.0-amd64-amd64.161024-144409.base.img eos.vdi
```
https://www.pragmaticlinux.com/2020/09/how-to-increase-the-disk-size-in-a-virtualbox-virtual-machine/
When creating a Persistent Storage, I got:
```
Error: Tails is running from non-USB / non-SDIO device.
```
Probably something that could be fixed.
In both cases, users also have to remove `live-media=removable`. (#6397)
- [ ] Double-check whether we could workaround the need to remove `live-media=removable`.
Stats from WhisperBack reports in 2019 and 2020:
| | ISO | | VFAT | |
|--|-----|--|------|--|
| VirtualBox | 24 | 50% | 1 | 2% |
| QEMU | 12 | 25% | 11 | 23% |
| | | | 48 | |
* For QEMU where USB images are already available, half of users choose them despite not being the default download.
* Some people already running VirtualBox from a physical or virtual USB stick.
issue