Backport of Core PR 11638
Note: Some changes in the original PR will appear to be missing or
different due to changes in 35638ea8b and ce143f3048.
Original PR description:
fb00c45c3 [tests] Explicitly disallow support for p2p versions below 60001 (John Newbery) 3858aabbd [tests] Remove support for p2p alert messages (John Newbery) c0b127470 [tests] Remove support for bre-BIP31 ping messages (John Newbery) 2904e301c [tests] Remove dead code from mininode.py (John Newbery) Pull request description: This is the first part of #11518. It removes a ~150 lines of unused code from the mininode module: - remove unused `deliver_sleep_time` and `EarlyDisconnectError` code - remove support for pre-BIP31 ping messages - remove support for alert message - explicitly don't support p2p versions lower than 60001 Should be an easy ACK for reviewers. If all extended tests pass, then this code really was dead :) Tree-SHA512: 508e612ceb0b094250d18e75522d51e6b14cd069443050ba4af34d6f890c58721cb5653e8bc000b60635b9474d035b0dcd9c509c0dcdb3a7501df17b787f83b0