SDL3: Some updates/implementations of audio methods

[scbafk]

A return value is required when opening a default playback device:

    audio_device = SDL_OpenAudioDevice(SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK, NULL);

• Modifies openAudioDevice to return Error!AudioDeviceId instead of Error!void

Null is allowed, figured I'd update this.

• Modifies openAudioDeviceStream userdata parameter to be nullable

Some other methods I needed, figured I'd share them.

• Implements createAudioStream, bindAudioStream, and loadWAV