Dropping Python 3.10 support.

[charris]

We are scheduled to drop Python 3.10 support in NumPy 2.3. I will make a PR to get started on that, but
have noticed a few issues I have questions about:

@ngoldbaum numpy/_core/src/multiarray/stringdtype/static_string.c has a 3.10 workaround.
@seberg numpy/_core/include/numpy/numpyconfig.h NPY_FEATURE_VERSION needs update.
@r-devulap linux_simd.yml could probably use an update/rework.
@mattip can PyPy support 3.11 yet?

[ngoldbaum]

I think the comment in static_string.C is referring to the note about Python3.9 here: https://docs.python.org/3.12/c-api/arg.html#strings-and-buffers

But looking at the same docs for 3.13, it looks like I might have misunderstood, and we can actually remove all the Py_SSIZE_T_CLEAN macros after we remove support for Python 3.12.

[charris]

@ngoldbaum Feel free to push a comment update to #27862.

[r-devulap]

rdevulap linux_simd.yml could probably use an update/rework.

Is 3.12 the new recommended version?

[r-devulap]

Never mind, I just saw your PR :)