Add a file operations fuzzer into testing tool kit

[mwatts15]

There's an existing fuzzer on github (https://github.com/regehr/fs-fuzz) that does some of what I want, but it doesn't:

1. generate random file names/potentially invalid file names;
2. execute patterns that stress TagFS specifically;
3. doesn't extend at the level of adding a new fuzzing procedure -- only designed to extend at the level of adding new file system operations/operations on the level of a single file.