Preliminary Thinknode M4 Support (#8754)

* Preliminary Thinknode M4 Support

* oops

* Fix RF switch TX configuration

* trunk'd

* GPS fix for M4

* Battery handling and LED for M4

* Trunk

* Drop debug warnings

* Make Red LED notification

* Merge cleanup

* Make white LEDs flash during charge

---------

Co-authored-by: Jonathan Bennett <jbennett@incomsystems.biz>

src/power.h

@@ -130,6 +130,8 @@ class Power : private concurrency::OSThread
     bool lipoChargerInit();
     /// Setup a meshSolar battery sensor
     bool meshSolarInit();
+    /// Setup a serial battery sensor
+    bool serialBatteryInit();
 
   private:
     void shutdown();