feat: update dependencies and integrate skin manager

- Added `dartamp_skin` as a local dependency in `pubspec.yaml`.
- Updated `path_provider` to version ^2.1.5.
- Modified `test_driver/app.dart` to initialize `SkinManager` and pass it to `DartampApp`.
- Updated `generated_plugins.cmake` to include `jni` in the FFI plugin list.

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

linux/flutter/generated_plugins.cmake

@@ -9,6 +9,7 @@ list(APPEND FLUTTER_PLUGIN_LIST
 )
 
 list(APPEND FLUTTER_FFI_PLUGIN_LIST
+  jni
 )
 
 set(PLUGIN_BUNDLED_LIBRARIES)