Break circular dependency main โ txdb
Break the circular dependency between main and txdb by:
- Moving CBlockFileInfo from main.h to chain.h. I think this makes sense, as the other block-file stuff is there too.
- Moving CDiskTxPos from main.h to txdb.h. This type seems specific to txdb.
- Pass a functor insertBlockIndex to LoadBlockIndexGuts. This leaves it up to the caller how to insert block indices.