[FL-2432], [FL-2487] Rework bt keys load and save (#1139)

* bt keys: rework load and save with saved_struct
* bt: rename bt keys storage functions
* furi_hal_nfc: allow context switch during emilation
* bt settings: rework with saved struct
* infrared: replace file worker with dialogs and storage
* Core, Loader: fix thread allocation tracking, much better, so wow.

Co-authored-by: Aleksandr Kutuzov <alleteam@gmail.com>

applications/loader/loader_i.h

@@ -30,7 +30,6 @@ struct Loader {
     Submenu* debug_menu;
     Submenu* settings_menu;
 
-    size_t free_heap_size;
     volatile uint8_t lock_count;
 
     FuriPubSub* pubsub;