New approach to support RX-only mode more cleanly (#2908)

* Add enabled checks in ReceiverModel and TransmitterModel

* Move TX limit logic to TransmitterModel from radio API

* Add TX disable functionality and UI

firmware/common/message.hpp

@@ -146,6 +146,7 @@ class Message {
         SSTVRXPhaseSlant = 88,
         SSTVRXCalibration = 89,
         SubCarData = 90,
+        TXDisabled = 91,
         MAX
     };
 
@@ -1699,4 +1700,11 @@ class SubCarDataMessage : public Message {
     uint64_t data2 = 0;
 };
 
+class TXDisabledMessage : public Message {
+   public:
+    constexpr TXDisabledMessage()
+        : Message{ID::TXDisabled} {
+    }
+};
+
 #endif /*__MESSAGE_H__*/