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/Makefile.am

@@ -171,6 +171,7 @@ BITCOIN_CORE_H = \
   interfaces/ipc.h \
   interfaces/node.h \
   interfaces/wallet.h \
+  kernel/chainstatemanager_opts.h \
   key.h \
   key_io.h \
   logging.h \

src/bitcoin-chainstate.cpp

@@ -70,7 +70,10 @@ int main(int argc, char* argv[])
 
 
     // SETUP: Chainstate
-    ChainstateManager chainman{chainparams};
+    const ChainstateManager::Options chainman_opts{
+        chainparams,
+    };
+    ChainstateManager chainman{chainman_opts};
 
     auto rv = node::LoadChainstate(false,
                                    std::ref(chainman),

src/init.cpp

@@ -1421,7 +1421,10 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
     for (bool fLoaded = false; !fLoaded && !ShutdownRequested();) {
         node.mempool = std::make_unique<CTxMemPool>(node.fee_estimator.get(), mempool_check_ratio);
 
-        node.chainman = std::make_unique<ChainstateManager>(chainparams);
+        const ChainstateManager::Options chainman_opts{
+            chainparams,
+        };
+        node.chainman = std::make_unique<ChainstateManager>(chainman_opts);
         ChainstateManager& chainman = *node.chainman;
 
         const bool fReset = fReindex;

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

src/test/util/setup_common.cpp

@@ -164,7 +164,10 @@ ChainTestingSetup::ChainTestingSetup(const std::string& chainName, const std::ve
 
     m_cache_sizes = CalculateCacheSizes(m_args);
 
-    m_node.chainman = std::make_unique<ChainstateManager>(chainparams);
+    const ChainstateManager::Options chainman_opts{
+        chainparams,
+    };
+    m_node.chainman = std::make_unique<ChainstateManager>(chainman_opts);
     m_node.chainman->m_blockman.m_block_tree_db = std::make_unique<CBlockTreeDB>(m_cache_sizes.block_tree_db, true);
 
     // Start script-checking threads. Set g_parallel_script_checks to true so they are used.

src/test/validation_chainstate_tests.cpp

@@ -22,8 +22,11 @@ BOOST_FIXTURE_TEST_SUITE(validation_chainstate_tests, TestingSetup)
 //!
 BOOST_AUTO_TEST_CASE(validation_chainstate_resize_caches)
 {
-    const CChainParams& chainparams = Params();
-    ChainstateManager manager(chainparams);
+    const ChainstateManager::Options chainman_opts{
+        Params(),
+    };
+    ChainstateManager manager{chainman_opts};
+
     WITH_LOCK(::cs_main, manager.m_blockman.m_block_tree_db = std::make_unique<CBlockTreeDB>(1 << 20, true));
     CTxMemPool mempool;
 

src/validation.h

@@ -14,6 +14,7 @@
 #include <attributes.h>
 #include <chain.h>
 #include <chainparams.h>
+#include <kernel/chainstatemanager_opts.h>
 #include <consensus/amount.h>
 #include <deploymentstatus.h>
 #include <fs.h>
@@ -853,7 +854,10 @@ private:
     friend CChainState;
 
 public:
-    explicit ChainstateManager(const CChainParams& chainparams) : m_chainparams{chainparams} { }
+    using Options = ChainstateManagerOpts;
+
+    explicit ChainstateManager(const Options& opts)
+        : m_chainparams(opts.chainparams) {};
 
     const CChainParams& GetParams() const { return m_chainparams; }
     const Consensus::Params& GetConsensus() const { return m_chainparams.GetConsensus(); }