Option to automatically load compatible OpRoms after Emulator start

[andreiw]

Using the LoadOpRom logic in https://github.com/intel/MultiArchUefiPkg/issues/36, add a new build option that will enhance EmulatorDxe to load all compatible OpRom images in DriverBinding Start(). This is not useful when the emulator is built as part of firmware (PciBus won't even be started when the driver loads), but it does make using a standalone-built emulator on existing systems easier via sideloading.