[FL-935] Queue-based SD app cycle. File select widget. (#388)

* SD App: more specific sd api
* Gui: view dispatcher fix api documentation
* Gui: view holder thingy
* SD App: do not sleep when working with sd card bus
* SD App: queue-based lifecycle
* Assets: sd-card assets
* SD App: init file select api

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

applications/sd-filesystem/view_holder.h

@@ -0,0 +1,92 @@
+#pragma once
+
+#include <gui/view.h>
+#include <gui/gui.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct ViewHolder ViewHolder;
+
+/** 
+ * @brief Free callback type
+ */
+typedef void (*FreeCallback)(void* free_context);
+
+/** 
+ * @brief Back callback type
+ * @warning comes from GUI thread
+ */
+typedef void (*BackCallback)(void* back_context);
+
+/**
+ * @brief Allocate ViewHolder
+ * @return pointer to ViewHolder instance
+ */
+ViewHolder* view_holder_alloc();
+
+/**
+ * @brief Free ViewHolder and call Free callback
+ * @param view_holder pointer to ViewHolder
+ */
+void view_holder_free(ViewHolder* view_holder);
+
+/**
+ * @brief Set view for ViewHolder
+ * 
+ * @param view_holder ViewHolder instance
+ * @param view View instance
+ */
+void view_holder_set_view(ViewHolder* view_holder, View* view);
+
+/**
+ * @brief Set Free callback
+ * 
+ * @param view_holder ViewHolder instance
+ * @param free_callback callback pointer
+ * @param free_context callback context
+ */
+void view_holder_set_free_callback(
+    ViewHolder* view_holder,
+    FreeCallback free_callback,
+    void* free_context);
+
+/**
+ * @brief Free callback context getter. Useful if your Free callback is a module destructor, so you can get an instance of the module using this method.
+ * 
+ * @param view_holder ViewHolder instance
+ * @return void* free callback context
+ */
+void* view_holder_get_free_context(ViewHolder* view_holder);
+
+void view_holder_set_back_callback(
+    ViewHolder* view_holder,
+    BackCallback back_callback,
+    void* back_context);
+
+/**
+ * @brief Attach ViewHolder to GUI
+ * 
+ * @param view_holder ViewHolder instance
+ * @param gui GUI instance to attach to
+ */
+void view_holder_attach_to_gui(ViewHolder* view_holder, Gui* gui);
+
+/**
+ * @brief Enable view processing
+ * 
+ * @param view_holder 
+ */
+void view_holder_start(ViewHolder* view_holder);
+
+/**
+ * @brief Disable view processing
+ * 
+ * @param view_holder 
+ */
+void view_holder_stop(ViewHolder* view_holder);
+
+#ifdef __cplusplus
+}
+#endif