interfaces, refactor: Add more block information to block connected notifications

Add new interfaces::BlockInfo struct to be able to pass extra block
information (file and undo information) to indexes which they are
updated to use high level interfaces::Chain notifications.

This commit does not change behavior in any way.

src/kernel/chain.h

@@ -0,0 +1,19 @@
+// Copyright (c) 2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_KERNEL_CHAIN_H
+#define BITCOIN_KERNEL_CHAIN_H
+
+class CBlock;
+class CBlockIndex;
+namespace interfaces {
+struct BlockInfo;
+} // namespace interfaces
+
+namespace kernel {
+//! Return data from block index.
+interfaces::BlockInfo MakeBlockInfo(const CBlockIndex* block_index, const CBlock* data = nullptr);
+} // namespace kernel
+
+#endif // BITCOIN_KERNEL_CHAIN_H