* Remove orphan state wipe from UnloadBlockIndex.
As orphan state is now "network state", like in
d6ea737be19a0001e69e4e854eb1cef21523ea7a,
UnloadBlockIndex is only used during init if we end up reindexing
to clear our block state so that we can start over. However, at
that time no connections have been brought up as CConnman hasn't
been started yet, so all of the network processing state logic is
empty when its called.
* Move network-msg-processing code out of main to its own file
* Rename the remaining main.{h,cpp} to validation.{h,cpp}
