Add ChainstateManagerOpts, using as ::Options

[META] Although it seems like we don't need it for just one option,
       we're going to introduce another member to this struct *in the
       next commit*. In future patchsets for libbitcoinkernel decoupling
       it from ArgsManager, even more members will be added here.

src/kernel/chainstatemanager_opts.h

@@ -0,0 +1,22 @@
+// 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_CHAINSTATEMANAGER_OPTS_H
+#define BITCOIN_KERNEL_CHAINSTATEMANAGER_OPTS_H
+
+#include <cstdint>
+#include <functional>
+
+class CChainParams;
+
+/**
+ * An options struct for `ChainstateManager`, more ergonomically referred to as
+ * `ChainstateManager::Options` due to the using-declaration in
+ * `ChainstateManager`.
+ */
+struct ChainstateManagerOpts {
+    const CChainParams& chainparams;
+};
+
+#endif // BITCOIN_KERNEL_CHAINSTATEMANAGER_OPTS_H