Initiate magnetometer based compass calibration from button presses (#5553)

* Initiate magenetometer based compass calibration from button presses

- only active for BMX160 accelerometers on RAK_4631
- replace automatic calibration on power on with button triggered
  calibration
- set 5 presses to trigger 30s calibration
- set 6 presses to trigger 60s calibration (useful if unit is not
  handheld, ie vehicle mounted)
- show calibration time remaining on calibration alert screen

* Fix non RAK 4631 builds

- exclude changes from non RAK 4631 builds
- remove calls to screen when not present

* Fix build on RAK4631_eth_gw

- exclude all compass heading updates on variant without screen

---------

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

src/motion/AccelerometerThread.h

@@ -48,6 +48,13 @@ class AccelerometerThread : public concurrency::OSThread
         setIntervalFromNow(0);
     };
 
+    void calibrate(uint16_t forSeconds)
+    {
+        if (sensor) {
+            sensor->calibrate(forSeconds);
+        }
+    }
+
   protected:
     int32_t runOnce() override
     {