* T096, and Station G3: refactoring the 'FEM' prefs to variant-specific code

* CommonCLI: 'FEM' commands removed
* introduced static no-op attachDynamicPrefs() for all boards

variants/xiao_rp2040/XiaoRP2040Board.h

@@ -2,6 +2,7 @@
 
 #include <Arduino.h>
 #include <MeshCore.h>
+#include <helpers/KeyValueStore.h>
 
 /*
  * This board has no built-in way to read battery voltage.
@@ -30,6 +31,8 @@ public:
   void begin();
   uint8_t getStartupReason() const override { return startup_reason; }
 
+  void attachDynamicPrefs(KeyValueStore* prefs) { }  // no-op
+
 #ifdef P_LORA_TX_LED
   void onBeforeTransmit() override { digitalWrite(P_LORA_TX_LED, HIGH); }
   void onAfterTransmit() override { digitalWrite(P_LORA_TX_LED, LOW); }