petsc4py: Support building with Py_LIMITED_API

Lisandro Dalcinrequested to merge
dalcinl/petsc4py/py-limited-api into main

All this work should not go to waste.

I'm not sure whether it is worth to put this under CI testing at this time.

Closes #1764 (closed).

PS: I'm not sure how --with-petsc4py is currently working in core PETSc, but using the feature introduced in this MR, it would be possible to build petsc4py in such a way that the binary extension modules can work with any Python>=3.10. To enable the feature, at the time petsc4py's setup.py runs, the environment must have PETSC4PY_BUILD_PYSABI=1 set.

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