libwavpackenc: remove libwavpackenc wrapper

libwavpackenc: remove libwavpackenc wrapper

The manual states "there is virtually no reason to use that encoder.".

It supports less sample formats than the native encoder, is less efficient
than the native encoder and is also slower and pretty much remains untested.
libwavpack also isn't being fuzzed, which given that we plug the parameters
without any sanitizing them looks concerning.