Autodoc: Support typing_extensions.overload

[TeamSpen210]

Purpose

I noticed that autodoc was not able to recognise @typing_extensions.overload, so the extra signatures wouldn't appear. This PR makes pycode.parser able to detect this, also adding support for @typing_extensions.final since it has the same issue.

I'm not sure if VariableCommentPicker here is public or not, since I changed the attributes there to collect both possible names. If it is I could instead add another 3 attributes, but that's less elegant.

[AA-Turner]

Can you explain the .copy()? Previously it always created an empty list.

[TeamSpen210]

typing_final was a str | None before, I changed it to a list to store multiple seen names. This copies to avoid mutation. This is just a simplification compared to making an empty list, then extending it immediately.

[AA-Turner]

I'd prefer to be explicit and use an empty list. The .copy() makes local reasoning harder because the instance state might have been mutated elsewhere.

[TeamSpen210]

Not sure what you mean by mutation elsewhere, unless other code made it not a list. Could also do list(self.typing_final_names). Using an empty list would be something like:

final = []
for name in self.typing_final_names:
    final.append(name)

Which is pointlessly overcomplicated.

[AA-Turner]

Not sure what you mean by mutation elsewhere, unless other code made it not a list

Mainly the risk of having more entries than needed, becuase this is a list rather than a set. However I think making it a set would work?:

final = set(self.typing_final_names) | {f'{mod}.final' for mod in self.typing_mods}

[TeamSpen210]

Ah, yes it can be possible for the list to have multiple copies, but only if the user did imports multiple times. Changing everything to sets would fix that, I just didn't think that was common enough to be worth using sets, when they'd normally only hold up to 4 items.