* Refactor OPUS encoder for quality and speed.
Use OPUS low delay mode (https://www.opus-codec.org/docs/opus_api-1.1.3/group__opus__ctlvalues.html#ga592232fb39db60c1369989c5c5d19a07)
* Slightly tweak linear resample function and disable it on 48kHz input
* Rewrite OPUS encoder as a struct with some internal buffer
* Use OPUS 192Kbps preset by default
* Add encoder callback function on a full buffer
* Reuse OPUS output buffer
* Add write limiter for samples
