NIO: Implement directory listing

[jart]

Implement these methods:

  /**
   * Throws {@link UnsupportedOperationException} because this feature hasn't been implemented yet.
   */
  @Override
  public DirectoryStream<Path> newDirectoryStream(Path dir, Filter<? super Path> filter) {
    // TODO: Implement me.
    throw new UnsupportedOperationException();
  }

  /**
   * Throws {@link UnsupportedOperationException} because this feature hasn't been implemented yet.
   */
  @Override
  public PathMatcher getPathMatcher(String syntaxAndPattern) {
    // TODO: Implement me.
    throw new UnsupportedOperationException();
  }

[mziccard]

For bookkeeping: @jean-philippe-martin addressed the first part of this issue in #884.

[jean-philippe-martin]

For the path matcher, would we be fine reusing the default one? The paths looks like normal paths, and I'd expect users want to use globs just like on a normal filesystem.

[garrettjonesgoogle]

It looks like #1469 solved this issue, so closing it out.