Large code re-organization which separates some key tasks in the rx

code.

Tested with X8R in SBus and PWM, and Spek Sat, GR-24 PPM, PWM and SUMD,
Spek PPM

src/test/unit/rx_ranges_unittest.cc

@@ -162,6 +162,11 @@ bool isPPMDataBeingReceived(void)
     return false;
 }
 
+bool isPWMDataBeingReceived(void)
+{
+    return false;
+}
+
 void resetPPMDataReceivedState(void)
 {
 }