Stash radio settings per app (#1151)

* add a little Stash utility.
* add radio state RAII helper.
* first part of radio_state changes
* add radio_state_ to rest of apps
* fix freq_step and format
* fix unused ui_sigfrx: corrected sample rate, added back freq setting

firmware/application/apps/lge_app.hpp

@@ -30,6 +30,7 @@
 #include "transmitter_model.hpp"
 #include "portapack.hpp"
 #include "app_settings.hpp"
+#include "radio_state.hpp"
 
 namespace ui {
 
@@ -49,6 +50,10 @@ class LGEView : public View {
         ALL
     };
 
+    TxRadioState radio_state_{
+        1750000 /* bandwidth */,
+        2280000 /* sampling rate */
+    };
     app_settings::SettingsManager settings_{
         "tx_lge", app_settings::Mode::TX};