fadfd84 test: Remove unused connect_nodes_bi (MarcoFalke)
fa3b9ee scripted-diff: test: Replace connect_nodes_bi with connect_nodes (MarcoFalke)
faaee1e test: Use connect_nodes when connecting nodes in the test_framework (MarcoFalke)
1111bb9 test: Reformat python imports to aid scripted diff (MarcoFalke)

Pull request description:

  By default all test nodes are connected in a chain. However, instead of just a single connection between each pair of nodes, we end up with up to four connections for a "middle" node (two outbound, two inbound, from each side).

  This is generally redundant (tx and block relay should succeed with just a single connection) and confusing. For example, test timeouts after a call to `sync_` may be racy and hard to reproduce. On top of that, the test `debug.log`s are hard to read because txs and block invs may be relayed on the same connection multiple times.

  Fix this by inlining `connect_nodes_bi` in the two tests that need it, and then replace it with a single `connect_nodes` in all other tests.

  Historic background:

  `connect_nodes_bi` has been introduced as a (temporary?) workaround for bug dashpay#5113 and dashpay#5138, which has long been fixed in dashpay#5157 and dashpay#5662.

ACKs for top commit:
  laanwj:
    ACK fadfd84
  jonasschnelli:
    utACK fadfd84 - more of less a cleanup PR.
  promag:
    Tested ACK fadfd84, ran extended tests.

Tree-SHA512: 2d027a8fd150749c071b64438a0a78ec922178628a7dbb89fd1212b0fa34febd451798c940101155d3617c0426c2c4865174147709894f1f1bb6cfa336aa7e24

fadfd84 test: Remove unused connect_nodes_bi (MarcoFalke)
fa3b9ee scripted-diff: test: Replace connect_nodes_bi with connect_nodes (MarcoFalke)
faaee1e test: Use connect_nodes when connecting nodes in the test_framework (MarcoFalke)
1111bb9 test: Reformat python imports to aid scripted diff (MarcoFalke)

Pull request description:

  By default all test nodes are connected in a chain. However, instead of just a single connection between each pair of nodes, we end up with up to four connections for a "middle" node (two outbound, two inbound, from each side).

  This is generally redundant (tx and block relay should succeed with just a single connection) and confusing. For example, test timeouts after a call to `sync_` may be racy and hard to reproduce. On top of that, the test `debug.log`s are hard to read because txs and block invs may be relayed on the same connection multiple times.

  Fix this by inlining `connect_nodes_bi` in the two tests that need it, and then replace it with a single `connect_nodes` in all other tests.

  Historic background:

  `connect_nodes_bi` has been introduced as a (temporary?) workaround for bug dashpay#5113 and dashpay#5138, which has long been fixed in dashpay#5157 and dashpay#5662.

ACKs for top commit:
  laanwj:
    ACK fadfd84
  jonasschnelli:
    utACK fadfd84 - more of less a cleanup PR.
  promag:
    Tested ACK fadfd84, ran extended tests.

Tree-SHA512: 2d027a8fd150749c071b64438a0a78ec922178628a7dbb89fd1212b0fa34febd451798c940101155d3617c0426c2c4865174147709894f1f1bb6cfa336aa7e24