Update net-p2p/go-ethereum to 1.8.0

Requires go version >= 1.9.2

Reliable light client
Reliable fast sync
Custom tracing scripts
Native events using abigen

Breaking changes:
Trie pruning is enabled on all --syncmode variations (including
--syncmode=full). If running an archive node, to retain historic data,
disable pruning with --gcmode=archive

PR: 225916
Submitted by: Enrique Fynn (maintainer)