Autoencoder world model tuning grid.

def next_frame_ae_range(rhp):
  """Autoencoder world model tuning grid."""
  rhp.set_float("dropout", 0.3, 0.5)
  rhp.set_int("num_compress_steps", 1, 3)
  rhp.set_int("num_hidden_layers", 2, 6)
  rhp.set_float("learning_rate_constant", 1., 2.)
  rhp.set_float("initializer_gain", 0.8, 1.5)
  rhp.set_int("filter_double_steps", 2, 3)