There is a possible data race/panic between processBlockchainCh and
processPeerUpdates, since when we send to blockchainCh.Out in one
goroutine and close the channel in the other. The race is seen in some
Github Action runs.
This commit fix the race, by adding a peerUpdatesCh as a bridge between
processPeerUpdates and processBlockchainCh, so the former will send to
this channel, the later will listen and forward the message to
blockchainCh.Out channel.
Updates #6516
