Move edk2-shell UEFI shell to root

Some motherboards can apparently load a UEFI shell directly from the root of a device if the file is /shellx64.efi.

To simplify our setup further this could be the better alternative and work for a set of mainboards out of the box (without requiring to even go via the bootloader).

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information