Add per-module state handling and API to PyModule

[Copilot]

The VM lacked a consistent module-level state mechanism analogous to CPython’s PyModule_GetState.

• API: Added PyModule::get_state and get_or_try_init_state, storing state behind a PyRwLock<Option<PyObjectRef>>, initializing under a write lock, and raising TypeError on incompatible existing state.
• Behavior: Documented semantics (returns None if absent or wrong type; init invoked only once). Improved error messaging for mismatched state types.
• Tests: Added a unit test ensuring per-module isolation, reuse of initialized state, and type-mismatch error behavior.

Example:

let state = module.get_or_try_init_state(vm, |vm| Ok(vm.ctx.new_int(1)))?; // init once
assert!(module.get_state::<PyInt>().is_some());                            // retrieve

Original prompt

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This section details on the original issue you should resolve

<issue_title>[RFC] module state for PyModule or builtin module</issue_title>
<issue_description>## Summary

related CPython function: PyModule_GetState
We are handling them with sometimes module attr and the other times static variable.

Detailed Explanation

Drawbacks, Rationale, and Alternatives

Unresolved Questions

</issue_description>

<agent_instructions>Investigate how CPython handle module state and try to add one</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes [RFC] module state for PyModule or builtin module #4054

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