Implement Python Import Caching

[mxwli]

py::module::import("module").attr("attribute");

becomes

kuzu::pycache::import_cache->module.attribute();

Now that modules are shared, it's required to acquire the Global Interpreter Lock before accessing modules.

Technically, it's possible to skip acquiring this lock if we know the module is already cached, but that isn't implemented here.

[codecov]

Codecov Report

Attention: Patch coverage is 97.10145% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 93.49%. Comparing base (93fc6e2) to head (9e9e381).
Report is 2 commits behind head on master.

Files	Patch %	Lines
...api/src_cpp/include/cached_import/py_cached_item.h	50.00%	1 Missing ⚠️
.../src_cpp/include/cached_import/py_cached_modules.h	95.65%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2905   +/-   ##
=======================================
  Coverage   93.48%   93.49%           
=======================================
  Files        1116     1121    +5     
  Lines       42717    42759   +42     
=======================================
+ Hits        39936    39978   +42     
  Misses       2781     2781           

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[Riolku]

Not a comprehensive list, but these are some copies I think, and they need to hold the GIL,.