Merge #11772: [tests] Change invalidblockrequest to use BitcoinTestFramework

Summary:
PR11772 backport https://github.com/bitcoin/bitcoin/pull/11772/files
e97b113b04 [tests] Change invalidblockrequest to use BitcoinTestFramework (John Newbery)
2b7064eda7 [tests] Fix flake8 warnings in invalidblockrequest (John Newbery)
54b8c580b7 [test] Fix nits leftover from 11771 (Conor Scott)

Pull request description:

Builds on #11771. Please review that PR first

Next step in #10603.

- first commit tidies up invalidblockrequest.py
- second commit removes usage of ComparisonTestFramework

Test Plan: test_runner.py

Reviewers: deadalnix, Fabien, jasonbcox, #bitcoin_abc

Reviewed By: deadalnix, #bitcoin_abc

Maniphest Tasks: T669

Differential Revision: https://reviews.bitcoinabc.org/D3511