MAINT: Add missing dtype overloads for object- and ctypes-based inputs

[charris]

Backport of #19468.

closes #19467

This PR modifies a number of overloads in the np.dtype constructor, adding support for the various
ctypes._SimpleCData subclasses. Secondly, it adds a catchall overload for Type[object] which was
previously missing.

Examples

import ctypes
import numpy as np
from typing import TYPE_CHECKING

dtype_object = np.dtype(object)
dtype_c_long = np.dtype(ctypes.c_long)

if TYPE_CHECKING:
    reveal_type(dtype_object)  # Revealed type is "numpy.dtype[numpy.object_]"
    reveal_type(dtype_c_long)  # Revealed type is "numpy.dtype[numpy.signedinteger[numpy.typing._64Bit]]"