Add the conv-transpose1d op. (#1251)

* Skeleton structure for conv-transpose1d.

* CPU implementation for conv-transpose1d.

candle-core/src/backend.rs

@@ -39,6 +39,14 @@ pub trait BackendStorage: Sized {
         _params: &crate::conv::ParamsConv1D,
     ) -> Result<Self>;
 
+    fn conv_transpose1d(
+        &self,
+        _l: &Layout,
+        _kernel: &Self,
+        _kernel_l: &Layout,
+        _params: &crate::conv::ParamsConvTranspose1D,
+    ) -> Result<Self>;
+
     fn conv2d(
         &self,
         _l: &Layout,