Do not use static type references when compiling for RustPython

[bschoenmaeckers]

Removed all usage of static type pointers when compiling for RustPython. Diff is large but is very repetitive.

Test plan

~/repo/pyo3 ❱ RUSTFLAGS="--cfg RustPython" cargo check
    Blocking waiting for file lock on build directory
    Checking pyo3-ffi v0.28.3 (/Users/basschoenmaeckers/repo/pyo3/pyo3-ffi)
    Checking pyo3 v0.28.3 (/Users/basschoenmaeckers/repo/pyo3)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 1.38s

xref RustPython/RustPython#7562

https://discuss.python.org/t/c-api-add-py-getbuildintype-and-py-getbuildintypeborrowed/107010

[codspeed-hq]

Merging this PR will not alter performance

✅ 105 untouched benchmarks
⏩ 1 skipped benchmark¹

---

_{Comparing bschoenmaeckers:RustPython-type-statics (bcbd085) with main (20246a8)}

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩

[davidhewitt]

There are a number of places in this PR where the extern blocks can be merged with one immediately above / below.

(I wonder if we could / should write a lint for that, maybe as part of the recently added machinery in the noxfile for formatting these?)

[bschoenmaeckers]

I've merged most adjacent blocks where the cfg attributes where the same. Please let me know I you see an other spot that needs cleaning.

[bschoenmaeckers]

I've moved around some some locally implemented/exported functions around to reduce even more extern_libpython blocks. Please let me know what you think.

[bschoenmaeckers]

I've also fixed all the places where link_name was not properly gated to PyPy only.

[davidhewitt]

Thanks, this seems reasonable to me

[bschoenmaeckers]

Thanks for reviewing this!