- net: Rename ::fRelayTxes to ::g_relay_txes
This helps to distinguish it from CNode::fRelayTxes and avoid bugs like
425278d17bd0edf8a3a7cc81e55016f7fd8e7726
- test: Format predicate source as multiline on error
- test: Add test for p2p_blocksonly
- doc: Mention blocksonly in reduce-traffic.md, unhide option
This is a backport of Core PR15990