Add ChainstateManager::m_adjusted_time_callback

This decouples validation.cpp from netaddress.cpp (transitively,
timedata.cpp, and asmap.cpp).

This is important for libbitcoinkernel as:

- There is no reason for the consensus engine to be coupled with
  netaddress, timedata, and asmap
- Users of libbitcoinkernel can now easily supply their own
  std::function that provides the adjusted time.

See the src/Makefile.am changes for some satisfying removals.

src/validation.h

@@ -362,6 +362,7 @@ bool TestBlockValidity(BlockValidationState& state,
                        CChainState& chainstate,
                        const CBlock& block,
                        CBlockIndex* pindexPrev,
+                       const std::function<int64_t()>& adjusted_time_callback,
                        bool fCheckPOW = true,
                        bool fCheckMerkleRoot = true) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
@@ -837,6 +838,8 @@ private:
 
     const CChainParams& m_chainparams;
 
+    const std::function<int64_t()> m_adjusted_time_callback;
+
     //! Internal helper for ActivateSnapshot().
     [[nodiscard]] bool PopulateAndValidateSnapshot(
         CChainState& snapshot_chainstate,
@@ -857,7 +860,8 @@ public:
     using Options = ChainstateManagerOpts;
 
     explicit ChainstateManager(const Options& opts)
-        : m_chainparams(opts.chainparams) {};
+        : m_chainparams{opts.chainparams},
+          m_adjusted_time_callback{Assert(opts.adjusted_time_callback)} {};
 
     const CChainParams& GetParams() const { return m_chainparams; }
     const Consensus::Params& GetConsensus() const { return m_chainparams.GetConsensus(); }