interfaces, refactor: Add more block information to block connected notifications

Add new interfaces::BlockInfo struct to be able to pass extra block
information (file and undo information) to indexes which they are
updated to use high level interfaces::Chain notifications.

This commit does not change behavior in any way.

src/Makefile.am

@@ -171,6 +171,7 @@ BITCOIN_CORE_H = \
   interfaces/ipc.h \
   interfaces/node.h \
   interfaces/wallet.h \
+  kernel/chain.h \
   kernel/chainstatemanager_opts.h \
   kernel/checks.h \
   kernel/coinstats.h \
@@ -365,6 +366,7 @@ libbitcoin_node_a_SOURCES = \
   index/coinstatsindex.cpp \
   index/txindex.cpp \
   init.cpp \
+  kernel/chain.cpp \
   kernel/checks.cpp \
   kernel/coinstats.cpp \
   kernel/context.cpp \