[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/gui/modules/file_browser_worker.h

@@ -0,0 +1,55 @@
+#pragma once
+
+#include "m-string.h"
+#include <gui/view.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct BrowserWorker BrowserWorker;
+typedef void (*BrowserWorkerFolderOpenCallback)(
+    void* context,
+    uint32_t item_cnt,
+    int32_t file_idx,
+    bool is_root);
+typedef void (*BrowserWorkerListLoadCallback)(void* context, uint32_t list_load_offset);
+typedef void (*BrowserWorkerListItemCallback)(
+    void* context,
+    string_t item_path,
+    bool is_folder,
+    bool is_last);
+typedef void (*BrowserWorkerLongLoadCallback)(void* context);
+
+BrowserWorker* file_browser_worker_alloc(string_t path, const char* filter_ext, bool skip_assets);
+
+void file_browser_worker_free(BrowserWorker* browser);
+
+void file_browser_worker_set_callback_context(BrowserWorker* browser, void* context);
+
+void file_browser_worker_set_folder_callback(
+    BrowserWorker* browser,
+    BrowserWorkerFolderOpenCallback cb);
+
+void file_browser_worker_set_list_callback(
+    BrowserWorker* browser,
+    BrowserWorkerListLoadCallback cb);
+
+void file_browser_worker_set_item_callback(
+    BrowserWorker* browser,
+    BrowserWorkerListItemCallback cb);
+
+void file_browser_worker_set_long_load_callback(
+    BrowserWorker* browser,
+    BrowserWorkerLongLoadCallback cb);
+
+void file_browser_worker_folder_enter(BrowserWorker* browser, string_t path, int32_t item_idx);
+
+void file_browser_worker_folder_exit(BrowserWorker* browser);
+
+void file_browser_worker_load(BrowserWorker* browser, uint32_t offset, uint32_t count);
+
+#ifdef __cplusplus
+}
+#endif