fix: preserve dict subclass types in _deepcopy_with_exceptions

[Jah-yee]

Summary

When copying dict subclasses (defaultdict, OrderedDict, Counter), the _deepcopy_with_exceptions function was returning a plain dict instead of preserving the type.

Bug

• defaultdict loses its default_factory
• OrderedDict becomes a regular dict
• Counter becomes a regular dict

Fix

The fix checks if the dict is a plain dict (type is dict) and uses the fast path. For subclasses, it creates a shallow copy, clears it, and repopulates with deep-copied values, preserving the subclass type.

if isinstance(obj, dict):
    if type(obj) is dict:
        return {k: _deepcopy_with_exceptions(v) for k, v in obj.items()}
    try:
        new = copy.copy(obj)
        new.clear()
        for k, v in obj.items():
            new[k] = _deepcopy_with_exceptions(v)
        return new
    except Exception:
        return {k: _deepcopy_with_exceptions(v) for k, v in obj.items()}
``"

Fixes #13092

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