Allow PyGraph and PyDiGraph to be annotated as generic classes at runtime

[IvanIsCoding]

Fixes #1345. It should address the core aspects for PyGraph and PyDiGraph. However, custom return types will come in a follow up PR

This makes the following work without requiring from __future__ import annotations:

import rustworkx as rx

graph: rx.PyDiGraph[int, int] = rx.PyDiGraph()

Also, this is worth highlighting: I refrained from adding __class_getitem__ to the type stubs as in the stubs that method is inherited from Generic[_S, _T] I ended up adding the method to the stubs as mypy stub tests disagreed with my reasoning

[coveralls]

Pull Request Test Coverage Report for Build 12661334236

Details

• 24 of 24 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 95.83%

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Totals
Change from base Build 12653809774:	0.005%
Covered Lines:	18384
Relevant Lines:	19184

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💛 - Coveralls