Improve fuzz testing infrastructure

[SWilson4]

There is still a lot of room for improvement when it comes to fuzzing liboqs. Unfortunately I only have a limited amount of bandwidth to work on this. If I get time over the weekend I'll put together a breif summary of where things are at currently, and where the remaining low hanging fruit is.

That being said I'm happy for you to close this issue. We have technically done the bulk of adding fuzz testing, everything from here on is mostly incremental improvements on the existing infrastructure.

Originally posted by @nathaniel-brough in #1215