WHL: build limited-api compliant wheels

[neutrinoceros]

Based off #371, similar to Unidata/netcdf4-python#1427
I've included a commit to drop support for 3.8 and 3.9 (soon to be EOL), but it can easily be split out of this PR if desired.

[neutrinoceros]

@jswhit I would recommend running CI on #371 first, and hopefully merge it, so I'll gain "contributor" privileges on this repo and will be able to iterate much faster on fixing CI here.

[neutrinoceros]

(that said, I think I found the issue and updated the branch here)

[neutrinoceros]

Here's the current error

ImportError: dlopen(/private/var/folders/y6/nj790rtn62lfktb1sh__79hc0000gn/T/cibw-run-67bztgcn/cp314-macosx_arm64/venv-test-arm64/lib/python3.14/site-packages/cftime/_cftime.abi3.so, 0x0002): symbol not found in flat namespace '_PyCode_NewWithPosOnlyArgs'

this is likely caused by some limitation (or bug) in Cython where it can still generate code that isn't strictly Limited-API-compliant. This is similar to why cp310-abi3 doesn't work, so let's try targeting cp312-abi3 instead

[neutrinoceros]

cp312-abi3 still errors (different symbol)

ImportError: dlopen(/private/var/folders/y6/nj790rtn62lfktb1sh__79hc0000gn/T/cibw-run-2th61c55/cp314-macosx_arm64/venv-test-arm64/lib/python3.14/site-packages/cftime/_cftime.abi3.so, 0x0002): symbol not found in flat namespace '__PyThreadState_UncheckedGet'

let's try cp313-abi3

[neutrinoceros]

cp313-abi3 builds fine and even passes tests on CPython 3.13, however it doesn't seem to survive the forward compatibility check on CPython 3.14:

2025-09-24T06:37:12.7224860Z + /bin/sh -c 'python -c "import cftime; print(f'"'"'cftime v{cftime.__version__}'"'"')" && python -m pytest -vv /Users/runner/work/cftime/cftime/test
2025-09-24T06:37:12.7225340Z '
2025-09-24T06:37:12.7535710Z <frozen importlib._bootstrap>:491: RuntimeWarning: compile time Python version 3.13 of module 'cftime._cftime' does not match runtime version 3.14

This again might be a sign of a limitation or bug in Cython, but I imagine it could also be a symptom of 3.14 not being completely stabilized yet (even though we're on rc3 at this point). I cannot do much more for now, I'll need to wait for the final 3.14.0 release, about 2 weeks from now, to see if anything changes.
If not, I'll report the 3 failure modes to Cython devs, and we'll see where it goes to from there.