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/init.cpp

@@ -1423,6 +1423,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
 
         const ChainstateManager::Options chainman_opts{
             chainparams,
+            GetAdjustedTime,
         };
         node.chainman = std::make_unique<ChainstateManager>(chainman_opts);
         ChainstateManager& chainman = *node.chainman;