DM: update launch scripts to use OVMF.fd directly from the rootfs

* Update the launch scripts provided as examples on how to launch a Zephyr,
VxWorks or Windows User VM to directly use the 'OVMF.fd' bios file installed
by default in '/usr/share/acrn/bios/'
* Remove the OVMF.fd that was kept under 'doc/tutorials' (no longer needed)
* Adapt the tutorials to reflect this change

Tracked-On: #3673
Signed-off-by: Geoffroy Van Cutsem <geoffroy.vancutsem@intel.com>

devicemodel/samples/nuc/launch_vxworks.sh

@@ -25,7 +25,7 @@ acrn-dm -A -m $mem_size -c $2 -s 0:0,hostbridge \
   -s 5,virtio-console,@stdio:stdio_port \
   -s 3,virtio-blk,./VxWorks.img \
   --virtio_poll 1000000 \
-  --ovmf ./OVMF.fd \
+  --ovmf /usr/share/acrn/bios/OVMF.fd \
   --lapic_pt \
   $vm_name
 }