Pre-import numpy lazy submodules before running tests

[SwayamInSync]

Workaround for an upstream CPython bug exposed by our free-threaded CI on cp3.14t.

Why

Our free-threaded CI on python3.14t started failing in test_pandas_strrep with a RecursionError whose entire stack was inside numpy/__init__.py's lazy __getattr__ recursing on import numpy.rec as rec. Root cause is a race in CPython's importlib._bootstrap: _load_unlocked clears spec._initializing = False before _find_and_load_unlocked runs setattr(parent_module, child, module), so the fast path in _find_and_load returns the module without the parent attribute under that window. Under free-threaded preemption a second thread reliably observes the window, falls into numpy's lazy __getattr__, runs import numpy.rec as rec again, fast-paths again, and recurses.

Upstream tracking:

• CPython issue: Free-threaded importlib race recurses on lazy-submodule __getattr__ python/cpython#149728
• CPython PR (fixes the race): gh-149728: Fix free-threaded race in importlib lazy-submodule fast path python/cpython#149729

Original failure traceback in this project's CI: #88 (comment)

[ngoldbaum]

This is fine but can you add a comment with a link to the upstream issue? Hopefully you'll be able to delete this when the next CPython bugfix release happens.

[SwayamInSync]

Yup will add comment to drop this in future

[SwayamInSync]

Merging this in