TODOs:
* symlink following behavior, trailing slash behavior (closely related to
  symlinks) in cap-std isnt ready yet.
* path_filestat_set_times, fd_filestat_set_times: different types used to set
  times for a Dir vs a File, this is a fs_set_times vs cap_fs_ext divergence
* File::set_fdflags is unimplemented, File::get_fdflags is lying - these are
  fcntl on unix, reopenfile / ?? on windows. Not implemented in system-interface yet.
* async scheduling!

wasi_tests::dangling_symlink
    - symlink following behavior 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::nofollow_errors
    - symlink following behavior not yet implemented
wasi_tests::path_filestat
    - fdstat.fs_flags is not populated correctly - APPEND | SYNC aren't
      present because File::get_fdflags isnt implemented correctly
wasi_tests::path_link
    - symlink following behavior not yet implemented
wasi_tests::path_rename_trailing_slashes
    - unclear, trailing slash behavior is wrong
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::remove_directory_trailing_slashes
    - apparently cap-std gives EINVAL when trying to remove dir with
      trailing slash?
wasi_tests::sched_yield
    - no sched yet