Add TRIO232: blocking sync call on file objects

[jakkdl]

A first draft at tracking types for file/path/httpx/etc and warning on sync calls. Except this one just does it for open() and the varios io.* types it can return as a start. This and others that build on top of it should finish off #58

Branched from on top of #103 - but you can just view the latest commit to see the contents of this one.

• The logic for tracking variables and their type will be moved to a superclass that different error_classes can inherit from (or possibly just implemented in Flake8TrioVisitor.
  • Child classes will probably be able to register calls and their return type so the superclass can use that. (so something like super().register('open', 'io.TextIOWrapper') in the __init__
  • code can then maybe be reused for the error classes tracking nurseries
• I don't think anybody in their right mind is going to send around io.TextIOWrapper objects to functions, but that's going to be much more common with Path and httpx objects, so I implemented it for this as well just to show the logic.
• Unless reimplemented as a plugin an top of a type checker this will ofc never be perfect, but handling Optional[Path] and Path|None will be done. list[Path] and similar cases can be done if it makes sense but I don't think will be common of any of the types we care about.
• I thiiink scope rules are handled correctly at the moment, but if that turns out to be tricky it can probably be dropped without worry.
• Code in general isn't super clean and will be rewritten, so don't bother with nitpicking much/at all

[Zac-HD]

Approach seems promising, agree that list[whatever] isn't worth handling but whatever|None probably is (if easy!). I look forward to seeing where this goes after rebasing 😁

[jakkdl]

Rebased on top of main (which wasn't trivial since it was forked from an outdated #103 that was later amended - fun stuff!). Will now continue working on it~

[jakkdl]

I'll refactor it in a different PR as I write the next object sync checker, as this one should work well as a standalone. Ready to merge!

[Zac-HD]

For the future refactored version, one annoying (to lint, it's fortunately rare) pattern is defining a httpx.Client() as a global variable...

[jakkdl]

For the future refactored version, one annoying (to lint, it's fortunately rare) pattern is defining a httpx.Client() as a global variable...

oh and it should work fine with global variables as long as they're defined in the same file. Will add tests to show that.

I'll make a PR just with these two fixes + another pattern I just realized will be useful:

async def type_assign():
    f: TextIOWrapper = ...
    f.read()