ggml : make ggml_is_view as API (#19539)

* make `ggml_is_view` as API

* introduce `ggml_aux_is_view` as inline version for internal use.

* change `ggml_aux_is_view` to  `ggml_impl_is_view`

ggml/src/ggml-impl.h

@@ -98,6 +98,10 @@ static bool ggml_op_is_empty(enum ggml_op op) {
     }
 }
 
+static inline bool ggml_impl_is_view(const struct ggml_tensor * t) {
+    return t->view_src != NULL;
+}
+
 static inline float ggml_compute_softplus_f32(float input) {
     return (input > 20.0f) ? input : logf(1 + expf(input));
 }