Move ::hashAssumeValid into ChainstateManager

This changes the assumed valid block for the bitcoin-chainstate
executable. Previously it was uint256{}, now it is defaultAssumeValid.

src/kernel/chainstatemanager_opts.h

@@ -5,10 +5,12 @@
 #ifndef BITCOIN_KERNEL_CHAINSTATEMANAGER_OPTS_H
 #define BITCOIN_KERNEL_CHAINSTATEMANAGER_OPTS_H
 
+#include <uint256.h>
 #include <util/time.h>
 
 #include <cstdint>
 #include <functional>
+#include <optional>
 
 class CChainParams;
 
@@ -24,6 +26,8 @@ namespace kernel {
 struct ChainstateManagerOpts {
     const CChainParams& chainparams;
     const std::function<NodeClock::time_point()> adjusted_time_callback{nullptr};
+    //! If set, it will override the block hash whose ancestors we will assume to have valid scripts without checking them.
+    std::optional<uint256> assumed_valid_block;
     //! If the tip is older than this, the node is considered to be in initial block download.
     std::chrono::seconds max_tip_age{DEFAULT_MAX_TIP_AGE};
 };