private static String newRandomFileSystemName() {
    return UUID.randomUUID().toString();
  }
Returns the system-loaded instance of {@code SystemJimfsFileSystemProvider} or {@code null} if
it could not be found or loaded.

<p>Like {@link FileSystems#newFileSystem(URI, Map, ClassLoader)}, this method first looks in
the list of {@linkplain FileSystemProvider#installedProviders() installed providers} and if not
found there, attempts to load it from the {@code ClassLoader} with {@link ServiceLoader}.

<p>The idea is that this method should return an instance of the same class (i.e. loaded by the
same class loader) as the class whose static cache a {@code JimfsFileSystem} instance will be
placed in when {@code FileSystems.newFileSystem} is called in {@code Jimfs.newFileSystem}.
jimfs/src/main/java/com/google/common/jimfs/Jimfs.java