Add the scatter in place ops. (#2923)

* Add the scatter_set op.

* Metal op.

* Cuda version.

* Merge the checks.

* Add the actual ops.

candle-core/tests/tensor_tests.rs

@@ -1087,6 +1087,18 @@ fn scatter(device: &Device) -> Result<()> {
             [1.0, 1.0, 1.0]
         ]
     );
+    init.scatter_set(&ids, &t, 0)?;
+    assert_eq!(
+        init.to_vec2::<f32>()?,
+        &[
+            [0.0, 10.0, 5.0],
+            [1.0, 1.0, 8.0],
+            [9.0, 1.0, 2.0],
+            [6.0, 7.0, 1.0],
+            [1.0, 4.0, 11.0],
+            [1.0, 1.0, 1.0]
+        ]
+    );
     Ok(())
 }