oniro-{image,linux}: use x-gpt-efi-disk for QEMU x86-64

Similar to how the SECO board was handled, the QEMU x86-64 machine can
now use EFI and GRUB correctly. This change is split over three parts,
MACHINE_FEATURES is modified to enable efi, WKS_FILE_DEPENDS to build
EFI firmware and lastly WKS_FILE to pick the new unified kick-start
file.

This was tested with:

        qemu-system-x86_64 -cpu IvyBridge -machine q35 -bios ovmf.qcow2 \
                oniro-image-base-qemux86-64.wic -m 1024 -nographic

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>