chore(dissect.cstruct): Get rid of Instance type annotation

[vlaci]

• It was already interpreted essentially the same way as typing.Any, because of its __getattr__ method
• Newer versions no longer have the Instance proxy object
• cstruct().<x> calls are annotated with Any in new versions
• The actual runtime type will be Structure in newer versions that needs to be changed in logging (not changed for now)

Relates-to: #888

[e3krisztian]

I did not like the Instance type annotations and celebrate its demise, as they were too generic to be meaningful, and what else do we have as values as type instances?

However instead of going explicitly Any (which is not really useful as a type annotation either for automated check or for human readers), I would prefer introducing a specific type alias for Any, by the name Structure or CStruct. Although it would not be much help as a machine checkable type annotation, but it would at least signal a type for the human reader.
After upgrading dissect.cstruct, the new Structure could be aliased/used instead.

[vlaci]

Unfortunately this Structure is sprinkled with so heavy metaclass magic¹, that even its __mro__ is unavailable as they are overwriting the instance dict directly... Fortunately, the isinstance(..., Structure) check will work for logging, but we won't be able to use it for type hints, as the generated fields are absent on the class definition.

Type-hinting with a custom Any type doesn't really add anything to it besides requiring extra imports for type annotations to work. I can add it though if you'd think it'd add any value

Footnotes

1. https://github.com/fox-it/dissect.cstruct/blob/7f6a584f77d48e8cce0ca11fd129b6f2a27e82a1/dissect/cstruct/types/structure.py#L367 ↩