Tracking Issue: Support for CPython subinterpreters in NumPy

[prathamhole14]

Description:
This issue tracks the architectural changes required to support CPython subinterpreters, to safely support multiple interpreters running simultaneously, NumPy must stop relying on global shared memory and ensure every interpreter gets its own distinct module instance.

Initial Roadmap:
Following CPython's Isolating Extension Modules guide, we will start with:

• ENH: Use multi-phase initialisation (PEP 489) for extension modules #29021 (This is an already on going effort by @AA-Turner)
• SubTracker: Move static variables into a struct and access them via PyModule_GetState. #31930
• Convert static types (PyTypeObject) to dynamically allocated heap types (PyType_FromModuleAndSpec).

Expected Outcomes for this phase:

• Core modules can be safely imported multiple times across different subinterpreters without memory leaks or race conditions.