node/chainstate: Decouple from concept of NodeContext

...instead pass in only the necessary information

Also allow mempool to be a nullptr

src/init.cpp

@@ -1421,7 +1421,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
         const int64_t load_block_index_start_time = GetTimeMillis();
         auto rv = LoadChainstate(fReset,
                                  chainman,
-                                 node,
+                                 node.mempool.get(),
                                  fPruneMode,
                                  chainparams,
                                  fReindexChainState,

src/node/chainstate.cpp

@@ -8,14 +8,13 @@
 #include <rpc/blockchain.h> // for RPCNotifyBlockChange
 #include <util/time.h> // for GetTime
 #include <node/blockstorage.h> // for CleanupBlockRevFiles, fHavePruned, fReindex
-#include <node/context.h> // for NodeContext
 #include <node/ui_interface.h> // for InitError, uiInterface, and CClientUIInterface member access
 #include <shutdown.h> // for ShutdownRequested
 #include <validation.h> // for a lot of things
 
 std::optional<ChainstateLoadingError> LoadChainstate(bool fReset,
                                                      ChainstateManager& chainman,
-                                                     NodeContext& node,
+                                                     CTxMemPool* mempool,
                                                      bool fPruneMode,
                                                      const CChainParams& chainparams,
                                                      bool fReindexChainState,
@@ -32,11 +31,11 @@ std::optional<ChainstateLoadingError> LoadChainstate(bool fReset,
     do {
         try {
             LOCK(cs_main);
-            chainman.InitializeChainstate(Assert(node.mempool.get()));
+            chainman.InitializeChainstate(Assert(mempool));
             chainman.m_total_coinstip_cache = nCoinCacheUsage;
             chainman.m_total_coinsdb_cache = nCoinDBCache;
 
-            UnloadBlockIndex(node.mempool.get(), chainman);
+            UnloadBlockIndex(mempool, chainman);
 
             auto& pblocktree{chainman.m_blockman.m_block_tree_db};
             // new CBlockTreeDB tries to delete the existing file, which

src/node/chainstate.h

@@ -10,7 +10,7 @@
 
 class CChainParams;
 class ChainstateManager;
-struct NodeContext;
+class CTxMemPool;
 
 enum class ChainstateLoadingError {
     ERROR_LOADING_BLOCK_DB,
@@ -55,7 +55,7 @@ enum class ChainstateLoadingError {
  */
 std::optional<ChainstateLoadingError> LoadChainstate(bool fReset,
                                                      ChainstateManager& chainman,
-                                                     NodeContext& node,
+                                                     CTxMemPool* mempool,
                                                      bool fPruneMode,
                                                      const CChainParams& chainparams,
                                                      bool fReindexChainState,