Add StorageRef. (#2113)

* Add the storage-ref bits.

* Add the metal implementation.

candle-core/src/tensor.rs

@@ -456,7 +456,15 @@ impl Tensor {
         shape: S,
         device: &Device,
     ) -> Result<Self> {
-        Self::new_impl(array, shape.into(), device, false)
+        let shape = shape.into();
+        let n: usize = shape.elem_count();
+        let buffer_size: usize = array.len();
+        if buffer_size != n {
+            return Err(Error::ShapeMismatch { buffer_size, shape }.bt());
+        }
+        let storage = device.storage_from_slice(array)?;
+        let none = BackpropOp::none();
+        Ok(from_storage(storage, shape, none, false))
     }
 
     pub(crate) fn same_shape_binary_op(&self, rhs: &Self, op: &'static str) -> Result<&Shape> {