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/stable-diffusion/resnet.rs

@@ -66,6 +66,7 @@ impl ResnetBlock2D {
             stride: 1,
             padding: 1,
             groups: 1,
+            dilation: 1,
         };
         let norm1 = nn::group_norm(config.groups, in_channels, config.eps, vs.pp("norm1"))?;
         let conv1 = conv2d(in_channels, out_channels, 3, conv_cfg, vs.pp("conv1"))?;
@@ -80,6 +81,7 @@ impl ResnetBlock2D {
                 stride: 1,
                 padding: 0,
                 groups: 1,
+                dilation: 1,
             };
             Some(conv2d(
                 in_channels,