Feature: inheritance checks for typed dictionaries

[yangdanny97]

These have special override/inheritance semantics

typeddicts have rules for redefining fields to add/remove qualifiers like ReadOnly, preventing conflicting field definitions from parents in multiple inheritance, etc.

There are two sub-tasks, either of which could be a good first issue:

• general typeddict inheritance rules: https://typing.python.org/en/latest/spec/typeddict.html#inheritance
• typeddict readonly inheritance rules: https://typing.python.org/en/latest/spec/typeddict.html#id3

Probably requires some special handling in this function: https://github.com/facebook/pyrefly/blob/9da3818099c6b0063a281b0a3ceb054363ad1de0/pyrefly/lib/alt/class/class_field.rs#L1057

[krikera]

Hey! I would like to work on this.

[yangdanny97]

@krikera great! let me know if you get stuck or have any questions :)

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[yangdanny97]

Marking this as up for grabs since there hasn't been any progress. If you're still working on it I could assign this back

[yangdanny97]

I believe this is complete based on the latest conformance results https://github.com/facebook/pyrefly/blob/main/conformance/third_party/results.json