Implement 'agc' reset for SX126x & LR11x0 chip families (#9705)

* Implement 'agc' reset for SX126x chip family

There's no actual agc on SX126x chips but you can reset the analog
registers by doing a warm sleep & running calibration.

* Address PR comments & implement for LR11x0 too

* calibrate for configured frequency band

* Gate LR11X0_AGC_RESET

src/mesh/SX126xInterface.h

@@ -28,6 +28,8 @@ template <class T> class SX126xInterface : public RadioLibInterface
 
     bool isIRQPending() override { return lora.getIrqFlags() != 0; }
 
+    void resetAGC() override;
+
     void setTCXOVoltage(float voltage) { tcxoVoltage = voltage; }
 
   protected: