Merge #11773: [tests] Change feature_block.py to use BitcoinTestFramework

265d7c4 [tests] Improve assert message when wait_until() fails (John Newbery)
ebf053a [tests] Change feature_block.py to use BitcoinTestFramework (John Newbery)
fc02c12 [tests] Add logging to feature_block.py (John Newbery)
3898c4f [tests] Tidy up feature_block.py (John Newbery)
5cd01d2 [tests] Fix flake8 warnings in feature_block.py (John Newbery)

Pull request description:

  Next step in #10603.

  - first three commits tidy up feature_block.py
  - fourth commit removes usage of ComparisonTestFramework

  Longer term, it would be better to separate net_processing testing from validation testing, but I think this is still a useful PR, since it moves us away from the comparison test framework.

Tree-SHA512: d0bb3ad22ad0aa1222877f4212bff075f9ce358e99c69c26d9913e4b346d931b8380e744434a9f6f37812c352cdaa75791691565bfeb18afcb619c06c6ca32a3

Author: laanwj