Move bitswap to its own crate (#12242)

* Introduce `sc-network-bitswap`

Move the bitswap protocol out of `sc-network` to its own crate.

* Improve test coverage

* Remove mention of bitswap from `sc-network`

* Fix documentation

* Fix clippy and remove the void dependency

* Remove unneeded trait bound and bump prost to 0.11

substrate/client/network/bitswap/src/schema.rs

@@ -0,0 +1,23 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2017-2022 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+//! Include sources generated from protobuf definitions.
+
+pub(crate) mod bitswap {
+	include!(concat!(env!("OUT_DIR"), "/bitswap.message.rs"));
+}