0.26 Release

[davidhewitt]

As proposed in #4390 (comment) I think we should proceed with 0.26 release so that we can then have a clean slate to release the changes to FromPyObject (and release those as 0.27 after some preparation).

Here's a selection of pieces which I think could be mergeable before release, with a bit of focus & support:

• rename Python::assume_gil_acquired to Python::assume_attached #5354
• add Python::try_attach #5342
• fix races when initializing #[pyclass] type objects #5341 will think more on the design for this one
• ci: run 3.14 on PR for the moment #5309
• Publish pyo3-introspection #5300
• add Bound::cast and friends #5289
• move #[pyclass] docstring generation to compile time #5286
• rename pyo3::prepare_freethreaded_python to Python::initialize #5247
• Allow naive datetime into chrono DateTime<Local> conversion #5178 (needs discussion see Allow naive datetime into chrono DateTime<Local> conversion #5178 (comment))
• add PyOnceLock type #5223 (and follow-up to disallow races when initializing types)
• fix crash when dropping PyBuffer after interpreter finalized #5242
• Report multiple errors from proc-macros #5159
• replace PyString::from_object with PyString::from_encoded_object #5017
• Towards soundness of PyByteArray::to_vec #4742
• Use disallow instantiation flag for classes without the __new__ method #4568
• Enable writing to python stdio streams #3920 (I think I'm not sure enough about the design on this one, will punt it for now, no need to rush)

... I'll start working to help those cross the line. Comment if anything else looks potentially relevant!

[Icxolu]

I think #5017 should also be pretty straight forward

[Tpt]

I would love to get #5300 to start easily playing with pyo3-introspection in Maturin (my hope is that we won't change to much the introspection format)

[davidhewitt]

I have added #5286 as a precursor to #5223 (motivated as a way to remove a needless use of some runtime global init in GILOnceCells)

[davidhewitt]

I think we're in a pretty good place to release soon; I still have #5223 underway, which we don't have to release with but I think would be nice given the general "reduce GIL in public API" theme of this release.

Also given that #5309 is flagging an issue with 3.14 testing we should check that and fixup before release.

Otherwise this release is looking good, thanks all who have contributed! 🙌

[davidhewitt]

#5342 (review) - need to add rename of assume_gil_acquired to match the rest of the renames.

[davidhewitt]

As per #5341 (comment) I would like to have a little bit longer to be sure about the semantics of race-free initialization, so I think we are ready to ship. #5367