[FL-2491] File browser GUI module (#1237)

* File browser module and test app
* nfc: Add support for saved files in subdirectories
* nfc: Use helper function to get shadow path when loading data
* File browser dialog integration pt.1
* File browser dialog integration pt.2
* Gui,Dialogs: drop file select
* Correct use of dynamic string_t(string_ptr)

Co-authored-by: Yukai Li <yukaili.geek@gmail.com>
Co-authored-by: Aleksandr Kutuzov <alleteam@gmail.com>

applications/applications.c

@@ -44,6 +44,7 @@ extern int32_t vibro_test_app(void* p);
 extern int32_t bt_hid_app(void* p);
 extern int32_t battery_test_app(void* p);
 extern int32_t text_box_test_app(void* p);
+extern int32_t file_browser_app(void* p);
 
 // Plugins
 extern int32_t music_player_app(void* p);
@@ -459,6 +460,14 @@ const FlipperApplication FLIPPER_DEBUG_APPS[] = {
      .flags = FlipperApplicationFlagDefault},
 #endif
 
+#ifdef APP_FILE_BROWSER_TEST
+    {.app = file_browser_app,
+     .name = "File Browser test",
+     .stack_size = 2048,
+     .icon = &A_BadUsb_14,
+     .flags = FlipperApplicationFlagDefault},
+#endif
+
 #ifdef APP_BATTERY_TEST
     {.app = battery_test_app,
      .name = "Battery Test",