message: Fix error code returned by some wasi fs syscalls for a non-existent file
  EINVAL should not be returned when a path name doesn't exist and should
  return ENOENT instead according to POSIX.
  This change affects to:
  path_filestat_get
  path_filestat_set_times
  path_link
  path_open
  path_readlink
  path_remove_directory
  path_unlink_file
diff: @@ -766,7 +766,7 @@ impl WasiFs {
  .fs_backing
  .symlink_metadata(&file)
  .ok()
  - .ok_or(__WASI_EINVAL)?;
  + .ok_or(__WASI_ENOENT)?;
  let file_type = metadata.file_type();
  // we want to insert newly opened dirs and files, but not transient symlinks
  // TODO: explain why (think about this deeply when well rested)
  @@ -894,7 +894,7 @@ impl WasiFs {
  {
  cur_inode = *entry;
  } else {
  - return Err(__WASI_EINVAL);
  + return Err(__WASI_ENOENT);
  }
  }
  Kind::File { .. } => {
  