reformat checklist #83

Copied out from #81

• Get rid of visitors manually visiting subnodes irrelevant with libcst

  • some possible solutions, either these two
    • exit_Xxx which is called for a node after it's subnodes have been visited (would clean up all cases of self.generic_visit(node) being used)
    • visit functions for node parts that in the AST don't have dedicated nodes, e.g. visit_Finally or visit_WhileElse. This would split up several long functions and solve the last cases of revisits - only trouble child would be 107_108.visit_loop, which explicitly wants to visit the body twice atm, but I could probably rewrite that
  • Or visitor classes implement a visit_Xxx as a pseudo-contextmanager, with enter and exit as magic names, and other names called as they match up with the _fields of the visited node. And the external runner handles a visit different depending on if it's isinstance function or class

• Split main file #103 I'm also starting to want to split up flake8_trio.py into different files, 1500 lines is starting to be quite inconvenient to navigate, and get any overview on - I also know you are hesitant to split given installation complications so would have to take care when doing that.

• runner now skips unselected visitors #91

• don't hard code unnecessary variables in Flake8TrioVisitor.get_state - it would most likely just mean renaming a lot of variables. But is bound to introduce bugs in it's current state so plan to fix it soon after merge.

• Move eval files into a separate directory #102 Move all trioxxx.py files into a subdirectory of tests/ so it's clear what files contains tests and which ones contain test data. Can then also get rid of regex and naming restrictions on files.