Integrate meta-seco-edgehog-things/ap/qemux86

Commit: edgehog/layers/seco/meta-seco-edgehog-things@644dfc09

[QEMU] add support for qemux86 and qemux86-64

• separate qemuarm and qemux86 WKS templates (different wic partitioning)
• use cpio.gz as initramfs format instead of cpio.gz.u-boot for qemux86*
• set grub as bootloader (PREFERRED_PROVIDER_virtual/bootloader has to be set in edgehog-base.inc otherwise it's empty and the utility grub-editenv doesn't get installed)
• mount sda1 as /boot (needed by grub-editenv, therefore by rauc, to update the grub environment)
• install grub.conf (rauc configuration)

To run Edgehog Things, you can't use the built-in QEMU legacy BIOS, SeaBIOS. You can download the OVMF bin (QEMU's UEFI bios) from here: https://www.kraxel.org/repos/jenkins/edk2/ Use ia32 for qemux86 and x64 for qemux86-64.

Use this command to run qemu:

BIOS=<path/to/OVMF.fd> runqemu [slirp] [nographic] [...]