Merge bitcoin/bitcoin#25487: [kernel 3b/n] Decouple `{Dump,Load}Mempool` from `ArgsManager`

cb3e9a1e3f8d72daaa361fc45dd853775e754b9d Move {Load,Dump}Mempool to kernel namespace (Carl Dong)
aa306765419f7dbea12b12e15553039835ba0e4d Move DEFAULT_PERSIST_MEMPOOL out of libbitcoinkernel (Carl Dong)
06b88ffb8ae7f2b2a93a32908cd80e77fafd270c LoadMempool: Pass in load_path, stop using gArgs (Carl Dong)
b857ac60d9a0433036519c26675378bbf56a1de1 test/fuzz: Invoke LoadMempool via CChainState (Carl Dong)
b3267258b052557fc136b9a4dcb754afb9219470 Move FopenFn to fsbridge namespace (Carl Dong)
ae1e8e37567fa603a5977d7d05105c682dd3f7db mempool: Use NodeClock+friends for LoadMempool (Carl Dong)
f9e8e5719f28d84f68f7d75e26c8e7fccac8e7d3 mempool: Improve comments for [GS]etLoadTried (Carl Dong)
813962da0b17b918941c6849996845e35d84a451 scripted-diff: Rename m_is_loaded -> m_load_tried (Carl Dong)
413f4bb52b72e082ad8716664ede48352b8e7e5a DumpMempool: Pass in dump_path, stop using gArgs (Carl Dong)
bd4407817e523e3c5b347bc6be25ed007cb27034 DumpMempool: Use std::chrono instead of weird int64_t arthmetics (Carl Dong)
c84390b741ab7b61c9f702d8b447c8cadc1257c8 test/mempool_persist: Test manual savemempool when -persistmempool=0 (Carl Dong)

Pull request description:

  This is part of the `libbitcoinkernel` project: #24303, https://github.com/bitcoin/bitcoin/projects/18

  -----

  This PR moves `{Dump,Load}Mempool` into its own `kernel/mempool_persist` module and introduces `ArgsManager` `node::` helpers in `node/mempool_persist_args`to remove the scattered calls to `GetBoolArg("-persistmempool", DEFAULT_PERSIST_MEMPOOL)`.

  More context can be gleaned from the commit messages.

  -----

  One thing I was reflecting on as I wrote this was that in the long run, I think we should probably invert the validation <-> mempool relationship. Instead of mempool not depending on validation, it might make more sense to have validation not depend on mempool. Not super urgent since `libbitcoinkernel` will include both validation and mempool, but perhaps something for the future.

ACKs for top commit:
  glozow:
    re ACK cb3e9a1e3f8d72daaa361fc45dd853775e754b9d via `git range-diff 7ae032e...cb3e9a1`
  MarcoFalke:
    ACK cb3e9a1e3f 🔒
  ryanofsky:
    Code review ACK cb3e9a1e3f8d72daaa361fc45dd853775e754b9d

Tree-SHA512: 979d7237c3abb5a1dd9b5ad3dbf3b954f906a6d8320ed7b923557f41a4472deccae3e8a6bca0018c8e7a3c4a93afecc502acd1e26756f2054f157f1c0edd939d

3 files changed, 33 insertions, 11 deletions

diff --git a/src/test/fuzz/mempool_utils.h b/src/test/fuzz/mempool_utils.h
new file mode 100644
index 0000000000..bfe12e30ba
--- /dev/null
+++ b/src/test/fuzz/mempool_utils.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_TEST_FUZZ_MEMPOOL_UTILS_H
+#define BITCOIN_TEST_FUZZ_MEMPOOL_UTILS_H
+
+#include <validation.h>
+
+class DummyChainState final : public CChainState
+{
+public:
+    void SetMempool(CTxMemPool* mempool)
+    {
+        m_mempool = mempool;
+    }
+};
+
+#endif // BITCOIN_TEST_FUZZ_MEMPOOL_UTILS_H
diff --git a/src/test/fuzz/tx_pool.cpp b/src/test/fuzz/tx_pool.cpp
index 2d88ee295b..63fbf0516a 100644
--- a/src/test/fuzz/tx_pool.cpp
+++ b/src/test/fuzz/tx_pool.cpp
@@ -8,6 +8,7 @@
 #include <node/miner.h>
 #include <test/fuzz/FuzzedDataProvider.h>
 #include <test/fuzz/fuzz.h>
+#include <test/fuzz/mempool_utils.h>
 #include <test/fuzz/util.h>
 #include <test/util/mining.h>
 #include <test/util/script.h>
@@ -34,15 +35,6 @@ struct MockedTxPool : public CTxMemPool {
     }
 };
 
-class DummyChainState final : public CChainState
-{
-public:
-    void SetMempool(CTxMemPool* mempool)
-    {
-        m_mempool = mempool;
-    }
-};
-
 void initialize_tx_pool()
 {
     static const auto testing_setup = MakeNoLogFileContext<const TestingSetup>();
diff --git a/src/test/fuzz/validation_load_mempool.cpp b/src/test/fuzz/validation_load_mempool.cpp
index 9532610f8d..90c1a71d9f 100644
--- a/src/test/fuzz/validation_load_mempool.cpp
+++ b/src/test/fuzz/validation_load_mempool.cpp
@@ -2,10 +2,14 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <kernel/mempool_persist.h>
+
 #include <chainparamsbase.h>
 #include <mempool_args.h>
+#include <node/mempool_persist_args.h>
 #include <test/fuzz/FuzzedDataProvider.h>
 #include <test/fuzz/fuzz.h>
+#include <test/fuzz/mempool_utils.h>
 #include <test/fuzz/util.h>
 #include <test/util/setup_common.h>
 #include <txmempool.h>
@@ -15,6 +19,10 @@
 #include <cstdint>
 #include <vector>
 
+using kernel::DumpMempool;
+
+using node::MempoolPath;
+
 namespace {
 const TestingSetup* g_setup;
 } // namespace
@@ -33,9 +41,12 @@ FUZZ_TARGET_INIT(validation_load_mempool, initialize_validation_load_mempool)
 
     CTxMemPool pool{MemPoolOptionsForTest(g_setup->m_node)};
 
+    auto& chainstate{static_cast<DummyChainState&>(g_setup->m_node.chainman->ActiveChainstate())};
+    chainstate.SetMempool(&pool);
+
     auto fuzzed_fopen = [&](const fs::path&, const char*) {
         return fuzzed_file_provider.open();
     };
-    (void)LoadMempool(pool, g_setup->m_node.chainman->ActiveChainstate(), fuzzed_fopen);
-    (void)DumpMempool(pool, fuzzed_fopen, true);
+    (void)chainstate.LoadMempool(MempoolPath(g_setup->m_args), fuzzed_fopen);
+    (void)DumpMempool(pool, MempoolPath(g_setup->m_args), fuzzed_fopen, true);
 }