Core Concepts (#262)

The most general concepts will be located in `mrc/core/concepts`. 

This PR added `core::concepts::not_void` which will be used quite broadly. It's first use will be in `channels::v2` as we never have a channel with a data type of `void`.

Authors:
  - Ryan Olson (https://github.com/ryanolson)

Approvers:
  - Michael Demoret (https://github.com/mdemoret-nv)

URL: #262

cpp/mrc/include/mrc/core/concepts/not_void.hpp

@@ -0,0 +1,30 @@
+/**
+ * SPDX-FileCopyrightText: Copyright (c) 2022, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <concepts>
+
+namespace mrc::core::concepts {
+
+template <typename T>
+concept not_void = requires
+{
+    requires not std::same_as<T, void>;
+};
+
+}  // namespace mrc::core::concepts