update objc2 crates

[httnn]

this pull request updates the objc2 ecosystem dependencies to their latest versions. the new versions include some useful features like being able to downcast NSObjects more easily.

most changes are due to renamed structs (Id -> Retained, WeakId -> Weak, NSArray::from_vec -> NSArray::from_retained_slice) and a slightly more streamlined way of defining new classes.

an open question: do we need to try to handle errors when working with CStrings or is unwrapping fine? i guess since CStrings are used only with class names unwrapping could be acceptable.

i have tested these changes to work but might be nice if someone else could confirm this as well.

[httnn]

oops i missed #508! there are no conflicts with main on here but feel free to close anyway. was luckily a very quick thing to do 😄

[DataTriny]

Sorry @httnn, it's always better to check for existing PRs before working on something. With that being said, I'll keep this one instead since it is more up to date. Thank you for your work!

Keep in mind however that like #508, we won't merge this until the next version of winit is released. We recognize that most of our users also have winit in their dependency tree and we want to avoid having multiple versions of objc2 related crates.

Thank you for your understanding.

[httnn]

i thought i did, but apparently not carefully enough, sorry about that!

is the reasoning that you just don't want to bloat the dependencies of projects that have both winit and accesskit as dependencies, or is there some technical compatibility issue?