Dilated convolutions (#657)

* Add the dilation parameter.

* Restore the basic optimizer example.

* Dilation support in cudnn.

* Use the dilation parameter in the cpu backend.

* More dilation support.

* No support for dilation in transposed convolutions.

* Add dilation to a test.

* Remove a print.

* Helper function.

candle-examples/examples/whisper/model.rs

@@ -281,11 +281,13 @@ impl AudioEncoder {
             padding: 1,
             stride: 1,
             groups: 1,
+            dilation: 1,
         };
         let cfg2 = Conv1dConfig {
             padding: 1,
             stride: 2,
             groups: 1,
+            dilation: 1,
         };
         let conv1 = conv1d(cfg.num_mel_bins, n_state, 3, cfg1, vb.pp("conv1"))?;
         let conv2 = conv1d(n_state, n_state, 3, cfg2, vb.pp("conv2"))?;