Stubbed Media and LibVLC classes

Used Abstract Factory Manager design pattern for LibVLC components

Tests done: StreamsModel, SubtitlesModel, HistoryModel, FilePickerModel,
       BrowserModel, StorageModel, FileBrowserModel, NetworkModel,
       VideosViewModel

Used CoroutineContextProvider to replace context on-demand.
Added extension function for the child of SingletonHolder used in ExternalSubRepository.
Replaced OpenSubtitleRepository.getInstance to use lazy value, so it can be replaced in tests.
Added Dependency Provider for BrowserProvider
Updated StubDataSource to configure data set to provide
LibVLC: Refactored interfaces

Signed-off-by: Shivansh Saini <shivanshs9@gmail.com>