Remove the dependency on Fulcrum and pytest-docker, and get all the benefits from the monorepo by testing with an up-to-date Chronik Electrum server.
The tests are now run on CI when electrum or chronik-http code is modified.
Potential future improvements that are out of scope for this diff:
- reuse more features from the node's test framework (`assert_equal`, `wait_until`...)
- provide more feedback on test failure (path the node's debug log and stderr...)
- provide less feedback on test success: don't log Electrum ABC's verbose output unconditionally, write it to a file
Depends on D18295