♻️ Extract file backend into utils subpackage

src/file_backend_stub.mbt

@@ -1,51 +1,37 @@
-pub struct FileHandle {
-  path : String
+pub type FileHandle = @utils.FileHandle
+
+pub fn open_file_handle_internal(path : String, append : Bool) -> FileHandle? {
+  @utils.open_file_handle_internal(path, append)
 }
 
-fn open_file_handle_internal(path : String, append : Bool) -> FileHandle? {
-  ignore(append)
-  ignore(path)
-  let _unused : FileHandle = { path: "" }
-  ignore(_unused)
-  None
+pub fn write_file_handle_internal(handle : FileHandle, content : String) -> Bool {
+  @utils.write_file_handle_internal(handle, content)
 }
 
-fn write_file_handle_internal(handle : FileHandle, content : String) -> Bool {
-  ignore(handle)
-  ignore(content)
-  false
+pub fn flush_file_handle_internal(handle : FileHandle) -> Bool {
+  @utils.flush_file_handle_internal(handle)
 }
 
-fn flush_file_handle_internal(handle : FileHandle) -> Bool {
-  ignore(handle)
-  false
+pub fn close_file_handle_internal(handle : FileHandle) -> Bool {
+  @utils.close_file_handle_internal(handle)
 }
 
-fn close_file_handle_internal(handle : FileHandle) -> Bool {
-  ignore(handle)
-  false
+pub fn file_size_internal(handle : FileHandle) -> Int {
+  @utils.file_size_internal(handle)
 }
 
-fn file_size_internal(handle : FileHandle) -> Int {
-  ignore(handle)
-  0
+pub fn rename_file_internal(from_path : String, to_path : String) -> Bool {
+  @utils.rename_file_internal(from_path, to_path)
 }
 
-fn rename_file_internal(from_path : String, to_path : String) -> Bool {
-  ignore(from_path)
-  ignore(to_path)
-  false
+pub fn remove_file_internal(path : String) -> Bool {
+  @utils.remove_file_internal(path)
 }
 
-fn remove_file_internal(path : String) -> Bool {
-  ignore(path)
-  false
+pub fn string_byte_length_internal(content : String) -> Int {
+  @utils.string_byte_length_internal(content)
 }
 
-fn string_byte_length_internal(content : String) -> Int {
-  content.length()
-}
-
-fn native_files_supported_internal() -> Bool {
-  false
+pub fn native_files_supported_internal() -> Bool {
+  @utils.native_files_supported_internal()
 }