Add service process for out of process compositing
This isn't quite ready just yet, but please have a look and provide any comments.
This is the output should the user have not launched the service.
xrt_instance_create - Failed to connect to monado sevice process
###
#
# Please make sure that the service procss is running
#
# It is called "monado-service"
# For builds it's located "build-dir/src/xrt/targets/service/monado-service"
#
###
XR_ERROR_RUNTIME_FAILURE in xrCreateInstance: Failed to create prober
Error [GENERAL | xrCreateInstance | OpenXR-Loader] : LoaderInstance::CreateInstance chained CreateInstance call failed