core: update blockProcFeed in insertChain

[zsfelfoldi]

This PR moves the updating of the blockProcFeed event feed from InsertChain to insertChain in order to ensure that the feed subscribers are notified whenever block processing happens.
Note that this event is not subscribed to anywhere in our codebase at the moment, earlier it was used by the LES server to avoid slowing down block processing. Now I want to do the same with the log indexer, the problem is that back then every block insertion was done by InsertChain, now the regular payload insertion is done by InsertBlockWithoutSetHead. Both of these (and also SetCanonical if needed) calls insertChain so I moved the feed update there.

[rjl493456442]

Unfortunately, the insertChain might be called by itself via insertSideChain, or via recoverAncestors.

The event stream could be something like this:

Process: True, Process: True, Process: false, Process: True, Process: false, Process: false