Add a simple player example to tools

The goal of this MR is to add a simple player example to tools.

This is currently not finished and WIP, do not merge it yet! It uses SDL2 for rendering for now and therefore only supports i420 8bit.

Todo:

• Do not allocate a new texture for each frame
• Add support for libplacebo rendering
• Add support for AV1 film grain when using libplacebo rendering
• Fix warnings
• Handle RGB properly?
• Add ability to configure threading