propolis should generate ACPI tables

[pfmooney]

We're stuck using an old (edk2-stable202105) version of OVMF, since it is the last one which featured a compiled-in set of ACPI tables which it presents to the guest OS. Subsequent versions of OVMF expect the vmm (read: qemu) to generate a set of ACPI tables and expose them via the fw_cfg table-loader interface. We should look to do the same so we can move to a newer bootrom.