Revert "refactor: we no longer need to treat 'class' lines specially"

This reverts commit 79f9f4575321fafc2ef770e3255f874db3d4b037.

Before these changes, these violations happened:

```
  lint run-test: commands[6] | python -m pylint --notes= coverage tests doc ci igor.py setup.py __main__.py
  ************* Module coverage.parser
  coverage/parser.py:1290 I: Useless suppression of 'too-many-function-args' (useless-suppression)
  ************* Module ci.download_gha_artifacts
  ci/download_gha_artifacts.py:18 W: Missing timeout argument for method 'requests.get' can cause your program to hang indefinitely (missing-timeout)
  ci/download_gha_artifacts.py:54 W: Missing timeout argument for method 'requests.get' can cause your program to hang indefinitely (missing-timeout)
  ************* Module ci.trigger_build_kits
  ci/trigger_build_kits.py:21 W: Missing timeout argument for method 'requests.post' can cause your program to hang indefinitely (missing-timeout)
  ************* Module ci.github_releases
  ci/github_releases.py:138 E: Too many positional arguments for function call (too-many-function-args)
  ci/github_releases.py:138 I: Useless suppression of 'no-value-for-parameter' (useless-suppression)
  ************* Module ci.comment_on_fixes
  ci/comment_on_fixes.py:30 W: Missing timeout argument for method 'requests.get' can cause your program to hang indefinitely (missing-timeout)
  ci/comment_on_fixes.py:37 W: Missing timeout argument for method 'requests.get' can cause your program to hang indefinitely (missing-timeout)
  ci/comment_on_fixes.py:49 W: Missing timeout argument for method 'requests.post' can cause your program to hang indefinitely (missing-timeout)
  ************* Module ci.parse_relnotes
  ci/parse_relnotes.py:126 E: Too many positional arguments for function call (too-many-function-args)
  ci/parse_relnotes.py:126 I: Useless suppression of 'no-value-for-parameter' (useless-suppression)
```

CPython added these lines in
https://github.com/python/cpython/commit/1bfe83a114da3939c00746fc44dc5da7f56f525f

Wrote this bug for pylint, because I shouldn't have to add a pragma:
https://github.com/PyCQA/pylint/issues/6592

See: https://bugs.python.org/issue46234

... and make some of them private.

Originally, this tokenizing code was paired with bytecode analysis.  But now we
use AST instead, so class lines don't need to be handled differently.