wasi_tests::big_random_buf
    - no randomness yet
wasi_tests::clock_time_get
    - no clocks yet
wasi_tests::dangling_symlink
    - Dir::open_dir nofollow not yet implemented
wasi_tests::directory_seek
    - something weird about directory open rights / fdstat. need debug
      impl of Caps to see about this
wasi_tests::fd_flags_set
    - set_fdflags is not implemented. test wanted to clear O_APPEND mode
wasi_tests::fd_readdir
    - test expects `..` and `.`, Dir::readdir doesnt provide them
wasi_tests::nofollow_errors
    - nofollow not implemented for dirs
wasi_tests::path_filestat
    - fdstat.fs_flags is not populated correctly
wasi_tests::path_link
    - path_link is not implemented
wasi_tests::path_rename
    - path_rename is not implemented. we need to be able to downcast a dyn
      WasiDir to a concrete Dir for this to be possible - need to reintroduce Any to hierarchy
wasi_tests::path_rename_trailing_slashes
    - path_rename is not implemented
wasi_tests::path_symlink_trailing_slashes
    - unclear, path_symlink is giving a ENOTDIR when it expects an EEXIST...
wasi_tests::poll_oneoff
    - no sched yet
wasi_tests::readlink
    - insists on small buffer semantics for readlink that don't seem right
wasi_tests::readlink_no_buffer
    - insists on small buffer semantics for readlink that don't seem right
wasi_tests::remove_directory_trailing_slashes
    - apparently cap-std gives EINVAL when trying to remove dir with
      trailing slash?
wasi_tests::sched_yield
    - no sched yet