Return status code instead of bool in IFrameEncoder & IFrameDecoder

[gavv]

Summary

audio::IFrameEncoder and audio::IFrameDecoder are interfaces for encoding and decoding of audio packets.

Currently they both have begin_frame() and end_frame() methods that don't return any errors. We need to update them to return status::StatusCode, so that they can report error if it happens.

Implementation

• Update IFrameEncoder and IFrameDecoder interfaces
• Update implementations:
  • audio::PcmEncoder
  • audio::PcmDecoder
• PCM encoder and decoder never fail, so they can just always return StatusOK. (Future implementation of IFrameEncoder and IFrameDecoder will be able to report errors, e.g. Opus)
• Update audio::Packetizer and audio::Depacketizer, which use IFrameEncoder and IFrameDecoder interfaces. When encoder or decoder return error, packetizer and depacketizer should forward it to upper level.

Testing

• Add unit test for Packetizer to check that it forwards error from encoder to upper level.
• Add unit test for Depacketizer to check that it forwards error from decoder to upper level.

[NSHABV]

Greetings, I would like to try my hand at this. Are there any more refactors planned for adjacent modules or am I free to fork master and begin developing this?