Add support for ffmpeg 6.0
- Use the new send_frame/receive_packet API for encoding
- Use the new channel layout API for audio
- Fix audio recording
- Copy codec parameters to the stream parameters
- Set correct pts for audio frames
- Read audio samples from file directly to the refcounted AVFrame buffer instead of the `g_pSamples` buffer
- Use global AVPackets allocated with `av_packet_alloc`
- Stop trying to write more audio frames when `WriteAudioFrame` fails with a negative error code
- Fix segfault with `g_pContainer->url`. The field has to be allocated with `av_malloc` before writing to it. It's set to `NULL` by default.
- Properly free allocations with `avcodec_free_context` and `avformat_free_context`
