Fix computed field inheritance with pydantic 2.13

[noamkush]

This fixes an issue we bumped into when trying to update to pydantic 2.13. See the tests - any use of computed_attr or computed_element in a base class results in an exception (on import). Both tests fail with current master branch. The implementation uses dataclasses.replace which differs from the base implementation to avoid repeating the many fields that need to be copied. This would probably be easier to maintain.

I used an LLM to make the code changes.

The error's stack trace looks like this

    class DerivedModel(SomeXmlBase, abc.ABC):
    ...<5 lines>...
  File "/home/noam/work/hl/django_app_be/.venv/lib/python3.14/site-packages/pydantic_xml/model.py", line 111, in __new__
    cls = typing.cast(Type['BaseXmlModel'], super().__new__(mcls, name, bases, namespace, **kwargs))
                                            ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/noam/work/hl/django_app_be/.venv/lib/python3.14/site-packages/pydantic/_internal/_model_construction.py", line 176, in __new__
    cls.__pydantic_decorators__ = DecoratorInfos.build(cls, replace_wrapped_methods=True)
                                  ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/noam/work/hl/django_app_be/.venv/lib/python3.14/site-packages/pydantic/_internal/_decorators.py", line 469, in build
    res.computed_fields.update({k: v.bind_to_cls(typ) for k, v in existing.computed_fields.items()})
                                   ~~~~~~~~~~~~~^^^^^
  File "/home/noam/work/hl/django_app_be/.venv/lib/python3.14/site-packages/pydantic/_internal/_decorators.py", line 289, in bind_to_cls
    info=copy(self.info),
         ~~~~^^^^^^^^^^^
  File "/home/noam/.local/share/uv/python/cpython-3.14.5-linux-x86_64-gnu/lib/python3.14/copy.py", line 82, in copy
    return copier(x)
  File "/home/noam/work/hl/django_app_be/.venv/lib/python3.14/site-packages/pydantic/fields.py", line 1588, in __copy__
    return type(self)(
           ~~~~~~~~~~^
        wrapped_property=self.wrapped_property,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<12 lines>...
        repr=self.repr,
        ^^^^^^^^^^^^^^^
    )
    ^
TypeError: ComputedXmlEntityInfo.__init__() missing 6 required positional arguments: 'location', 'path', 'ns', 'nsmap', 'nillable', and 'wrapped'

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.22%. Comparing base (d3c727f) to head (b9d8b4a).
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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #328   +/-   ##
=======================================
  Coverage   92.21%   92.22%           
=======================================
  Files          31       31           
  Lines        1786     1788    +2     
=======================================
+ Hits         1647     1649    +2     
  Misses        139      139           

Flag	Coverage Δ
unittests	92.22% <100.00%> (+<0.01%)	⬆️

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