Those fuzzers have been written and used internally with great results,
finding a couple of bugs, both in code and in design,
and have a code coverage of ~80% for the src/ folder,
and ~90% for both silk/ and celt/.
The fuzzers are put here and not upstream in libopus' repository,
because they are written in C++, and I'm not sure it's worth
the complexity of re-implementing FuzzedDataProvider
in C just for the sake of moving those files.
Co-authored-by: Julien Voisin <jvoisin@google.com>