Refactor app launching (#174)

- Refactor the way apps work: Instead of a C interface, they are now C++ classes. The main reasoning is that attaching data to an app was cumbersome. Having different implementations for different kinds of apps was cumbersome too. (3 or 4 layers of manifest nesting for the TactilityC project)
- External apps are still written in C, but they get a createData/destroyData in their manifest, so:
- External apps now have their own manifest.
- All functions in the original AppManifest are removed and replaced by a single `createApp` function
- External apps now automatically register (each app individually!) when they run the first time. As a side-effect they become visible in the `AppList` app!
- Adapted all apps for the new interface.
- Adapted all internal logic for these changes (Gui, ViewPort, Loader, AppContext, AppInstance, etc.)
- Rewrote parts of Loader to use std::shared_ptr to make the code much safer.
- Added a refcount check for the `AppInstance` and `App` at the end of their lifecycle. Show warning if refcount is too high.

Tactility/Source/service/gui/GuiDraw.cpp

@@ -9,9 +9,10 @@ namespace tt::service::gui {
 
 #define TAG "gui"
 
-static lv_obj_t* createAppViews(Gui* gui, lv_obj_t* parent, app::AppContext& app) {
+static lv_obj_t* createAppViews(Gui* gui, lv_obj_t* parent) {
     lv_obj_send_event(gui->statusbarWidget, LV_EVENT_DRAW_MAIN, nullptr);
     lv_obj_t* child_container = lv_obj_create(parent);
+    lv_obj_set_style_pad_all(child_container, 0, 0);
     lv_obj_set_width(child_container, LV_PCT(100));
     lv_obj_set_flex_grow(child_container, 1);
 
@@ -34,19 +35,17 @@ void redraw(Gui* gui) {
     if (lvgl::lock(1000)) {
         lv_obj_clean(gui->appRootWidget);
 
-        ViewPort* view_port = gui->appViewPort;
-        if (view_port != nullptr) {
-            app::AppContext& app = view_port->app;
+        if (gui->appToRender != nullptr) {
 
-            app::Flags flags = app.getFlags();
+            app::Flags flags = std::static_pointer_cast<app::AppInstance>(gui->appToRender)->getFlags();
             if (flags.showStatusbar) {
                 lv_obj_remove_flag(gui->statusbarWidget, LV_OBJ_FLAG_HIDDEN);
             } else {
                 lv_obj_add_flag(gui->statusbarWidget, LV_OBJ_FLAG_HIDDEN);
             }
 
-            lv_obj_t* container = createAppViews(gui, gui->appRootWidget, app);
-            view_port_show(view_port, container);
+            lv_obj_t* container = createAppViews(gui, gui->appRootWidget);
+            gui->appToRender->getApp()->onShow(*gui->appToRender, container);
         } else {
             TT_LOG_W(TAG, "nothing to draw");
         }