feat(types) Support for inline generics

[InvincibleRMC]

Description

https://github.com/pybind/pybind11/pull/5167

Expands upon the initial TypeVars to generate inline generics by putting typevars, paramspecs, or typevartuples, in the atrribute __type_params__ where using the python3.12 inline generic syntax stores them. This should work for functions and classes. For more info on __type_params__ can be found here.

Normal Python3.12 syntax.

def foo[T](x: T) -> T:
      return x

Mocked by doing the following in pybind.

def foo(x: T) -> T:
      return x
T = TypeVar('T')
foo.__type_params__ = T

Suggested changelog entry:

Adds support for generating inline generics with stubgen with `TypeVar`, `ParamSpec`, and `TypeVarTuple`

[InvincibleRMC]

Currently the following classes are seg faulting due to some error in their construction. Any ideas on how to properly create such classes? I tried some stuff with inheriting the constructor from object() but got nowhere. Another solution could be to replace the class with a function which just returns a python object with the attributes set but, I also got stuck with that idea. I'm sure both of these solutions are likely possible but, I'm not sure what I'm missing.

class ParamSpec : public object {
    PYBIND11_OBJECT_DEFAULT(ParamSpec, object, PyObject_Type)
    using object::object;
    ParamSpec(const char *name) {
        attr("__name__") = name;
        attr("__bound__") = pybind11::none();
    }
};

class TypeVarTuple : public object {
    PYBIND11_OBJECT_DEFAULT(TypeVarTuple, object, PyObject_Type)
    using object::object;
    TypeVarTuple(const char *name) { attr("__name__") = name; }
};

Error attached

[ 37%] Linking CXX shared module pybind11_tests.cpython-312-x86_64-linux-gnu.so
lto-wrapper: warning: using serial compilation of 6 LTRANS jobs
lto-wrapper: note: see the ‘-flto’ option documentation for more information
------ pybind11_tests.cpython-312-x86_64-linux-gnu.so file size: 393264 (no change)
[ 37%] Built target pybind11_tests
Segmentation fault (core dumped)
gmake[3]: *** [tests/CMakeFiles/pytest.dir/build.make:70: tests/CMakeFiles/pytest] Error 139
gmake[2]: *** [CMakeFiles/Makefile2:269: tests/CMakeFiles/pytest.dir/all] Error 2
gmake[1]: *** [CMakeFiles/Makefile2:330: tests/CMakeFiles/check.dir/rule] Error 2
gmake: *** [Makefile:222: check] Error 2