Warn if SYS_HITL is set

PX4 setup: Put sensors before radio to create the right affordance: We want the user to handle this first

This makes VehicleComponents reusable from core plugin without
requiring override of prerequisiteSetup

-closes #3274

Fact* espVersion = getFact(FactSystem::ParameterProvider, MAV_COMP_ID_UDP_BRIDGE, "SW_VER"); crashes unit test if the parameter does not exist (which is exactly what the call is trying to establish).

Refactored PX4 radio config to work with both PX4 and APM