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

cb3e9a1e3f Move {Load,Dump}Mempool to kernel namespace (Carl Dong)
aa30676541 Move DEFAULT_PERSIST_MEMPOOL out of libbitcoinkernel (Carl Dong)
06b88ffb8a LoadMempool: Pass in load_path, stop using gArgs (Carl Dong)
b857ac60d9 test/fuzz: Invoke LoadMempool via CChainState (Carl Dong)
b3267258b0 Move FopenFn to fsbridge namespace (Carl Dong)
ae1e8e3756 mempool: Use NodeClock+friends for LoadMempool (Carl Dong)
f9e8e5719f mempool: Improve comments for [GS]etLoadTried (Carl Dong)
813962da0b scripted-diff: Rename m_is_loaded -> m_load_tried (Carl Dong)
413f4bb52b DumpMempool: Pass in dump_path, stop using gArgs (Carl Dong)
bd4407817e DumpMempool: Use std::chrono instead of weird int64_t arthmetics (Carl Dong)
c84390b741 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 cb3e9a1e3f via `git range-diff 7ae032e...cb3e9a1`
  MarcoFalke:
    ACK cb3e9a1e3f 🔒
  ryanofsky:
    Code review ACK cb3e9a1e3f

Tree-SHA512: 979d7237c3abb5a1dd9b5ad3dbf3b954f906a6d8320ed7b923557f41a4472deccae3e8a6bca0018c8e7a3c4a93afecc502acd1e26756f2054f157f1c0edd939d

src/init.cpp

@@ -10,6 +10,7 @@
 #include <init.h>
 
 #include <kernel/checks.h>
+#include <kernel/mempool_persist.h>
 
 #include <addrman.h>
 #include <banman.h>
@@ -41,6 +42,7 @@
 #include <node/chainstate.h>
 #include <node/context.h>
 #include <node/interface_ui.h>
+#include <node/mempool_persist_args.h>
 #include <node/miner.h>
 #include <policy/feerate.h>
 #include <policy/fees.h>
@@ -102,14 +104,19 @@
 #include <zmq/zmqrpc.h>
 #endif
 
+using kernel::DumpMempool;
+
 using node::CacheSizes;
 using node::CalculateCacheSizes;
 using node::ChainstateLoadVerifyError;
 using node::ChainstateLoadingError;
 using node::CleanupBlockRevFiles;
+using node::DEFAULT_PERSIST_MEMPOOL;
 using node::DEFAULT_PRINTPRIORITY;
 using node::DEFAULT_STOPAFTERBLOCKIMPORT;
 using node::LoadChainstate;
+using node::MempoolPath;
+using node::ShouldPersistMempool;
 using node::NodeContext;
 using node::ThreadImport;
 using node::VerifyLoadedChainstate;
@@ -245,8 +252,8 @@ void Shutdown(NodeContext& node)
     node.addrman.reset();
     node.netgroupman.reset();
 
-    if (node.mempool && node.mempool->IsLoaded() && node.args->GetBoolArg("-persistmempool", DEFAULT_PERSIST_MEMPOOL)) {
-        DumpMempool(*node.mempool);
+    if (node.mempool && node.mempool->GetLoadTried() && ShouldPersistMempool(*node.args)) {
+        DumpMempool(*node.mempool, MempoolPath(*node.args));
     }
 
     // Drop transactions we were still watching, and record fee estimations.
@@ -1669,7 +1676,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
     }
 
     chainman.m_load_block = std::thread(&util::TraceThread, "loadblk", [=, &chainman, &args] {
-        ThreadImport(chainman, vImportFiles, args);
+        ThreadImport(chainman, vImportFiles, args, ShouldPersistMempool(args) ? MempoolPath(args) : fs::path{});
     });
 
     // Wait for genesis block to be processed