[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>

lib/toolbox/path.h

@@ -14,6 +14,15 @@ extern "C" {
  */
 void path_extract_filename_no_ext(const char* path, string_t filename);
 
+/**
+ * @brief Extract filename string from path.
+ * 
+ * @param path path string
+ * @param filename output filename string. Must be initialized before.
+ * @param trim_ext true - get filename without extension
+ */
+void path_extract_filename(string_t path, string_t filename, bool trim_ext);
+
 /**
  * @brief Extract last path component
  *