test: Replace use of (dis)?connect_nodes globals

Summary:
This is a 3 commit PR that replaces all uses of util.(dis)?connect_nodes with TestFramework.(dis)?connect_nodes. This reduces the number of imports by a lot and leave only one single way of doing this operation.

A later scripted-diff commit replaces the majority of uses, which all
follow this pattern:

`(dis)?connect_nodes(self.nodes[a], self.nodes[b]))`

This commit replaces the few "special cases".

This is a backport of core#19667 [1/3]
https://github.com/bitcoin/bitcoin/pull/19967/commits/be386840d4a394a1b6221fb7d0fa2b0bc4b1d413

The line touched in rpc_psbt is in a segwit related test that does not exist in Bitcoin ABC.

Test Plan: ninja check-functional

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10558