Use multiple FileWriter classes

[k4pran]

In the current implementation we have a single SceneFileWriter. This handles all formats, gifs, pngs, mp4 etc. Some of the flows are completely different such as writing images vs videos, and some are quite similar such as mp4 vs mov files.

The issue is that we have logic for all of them rolled into one class meaning that we are checking config for the format throughout - an example is

        if write_to_movie():
            movie_dir = guarantee_existence(
            ...

            if is_gif_format():
                self.gif_file_path = add_extension_if_not_present(
                    self.output_name, GIF_FILE_EXTENSION
                )
                ...

and

        if write_to_movie():
            self.writing_process.stdin.write(
                renderer.get_raw_frame_buffer_object_data(),
            )
        elif is_png_format() and not config["dry_run"]:
            target_dir = self.image_file_path.parent / self.image_file_path.stem
            ...

We also need special ffmpeg flags for different formats. This makes it difficult to follow and adds a lot of complexity. I propose having a base - FileWriterBase class with common functionality across all formats. We can then extend this once for videos VideoFileWriter and once for images -ImageFileWriter, and perhaps extend the video for different formats e.g. MP4Writer.

What this will allow us to do is to let Scene initialize the writer that is needed based on the format in config and from there on we will never need to check the format and all the logic for each format will be contained in the relevant classes.