feat: Add 'ord' option for PyClass and corresponding tests

[Zyell]

Updated the macros back-end to include 'ord' as an option for PyClass allowing for Python-style ordering comparison of enum variants. Additionally, test cases to verify the proper functioning of this new feature have been introduced.

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[Zyell]

I just pushed the changes I worked on over the weekend (sorry for the delay! It was a holiday weekend here, didn't get around to finalizing things until this morning) to support ordering for all enums and structs. I've updated tests and placed a note in the documentation. Compile time errors are also validated for when ParialOrd is not implemented and the ord argument is passed to the pyclass macro. I have made notes that additional checks for equality will be added when that is done. @Icxolu I will take a closer look at your PR to merge that. Edit: Found pyclass parameters documentation section, but let me know if additional updates should be made elsewhere.

[Zyell]

@Icxolu I am working on integrating ord now that eq has been merged. I was working on the tests and came across this case:

#[pyclass(eq_int)]
#[derive(Debug, Clone)]
pub enum MyEnumOrd {
    Variant,
    OtherVariant,
}

#[test]
fn test_simple_enum_ord_comparable() {
    Python::with_gil(|py| {
        let var1 = Py::new(py, MyEnumOrd::Variant).unwrap();
        let var2 = Py::new(py, MyEnumOrd::Variant).unwrap();
        py_assert!(py, var1 var2, "(var1 == var2) == True");
    })
}

This currently fails, but adding eq causes it to pass. There was a test in the test suite before with a similar test for which this was passing without eq or eq_int. If the goal is to retain the old behavior while issuing the deprecation warning, shouldn't the above test pass? Is this the expected behavior if only eq_int is passed? I ran this test on main to verify it wasn't some regression I introduced. The only difference I can see is in that no match arms are added, just the catchall remains, and the slot is generated differently here.

[Icxolu]

Oops, yeah that's a bug. Thanks for catching! It seem like I forgot the eq_int case in pyclass_richcmp_arms, I'll open a PR to fix 😇