…consensus-invalid txs

876dbdfb4702410dfd4037614dc9298a0c09c63e tests: drop expect_disconnect behaviour for tx relay (Anthony Towns)
b29ae9efdfeeff774e32ee433ce67d8ed8ecd49f validation: only check input scripts once (Anthony Towns)
266dd0e10d08c0bfde63205db15d6c210a021b90 net_processing: drop MaybePunishNodeForTx (Anthony Towns)

Pull request description:

  Because we do not discourage nodes for transactions we consider non-standard, we don't get any DoS protection from this check in adversarial scenarios, so remove the check entirely both to simplify the code and reduce the risk of splitting the network due to changes in tx relay policy.

  Then, because we no longer make use of the distinction between consensus and standardness failures during script validation, don't re-validate each script with only-consensus rules, reducing the cost to us of transactions that we won't relay.

ACKs for top commit:
  achow101:
    ACK 876dbdfb4702410dfd4037614dc9298a0c09c63e
  darosior:
    re-ACK 876dbdfb4702410dfd4037614dc9298a0c09c63e
  sipa:
    re-ACK 876dbdfb4702410dfd4037614dc9298a0c09c63e
  glozow:
    ACK 876dbdfb4702410dfd4037614dc9298a0c09c63e

Tree-SHA512: 8bb0395766dde54fc48f7077b80b88e35581aa6e3054d6d65735965147abefffa7348f0850bb3d46f6c2541fd384ecd40a00a57fa653adabff8a35582e2d1811