GH-42018: Add numpy.StringDType support #54893

Job	Run time
ARM64 macOS 14 Python 3	6m 59s
AMD64 macOS 15-intel Python 3	9m 42s
AMD64 Conda Python 3.10 Sphinx & Numpydoc	14m 42s
AMD64 Windows 2022 Python 3.13	5m 6s
AMD64 Conda Python 3.13 Pandas latest	3m 49s
AMD64 Conda Python 3.12 without NumPy	3m 14s
AMD64 Conda Python 3.10 Pandas 1.3.4	3m 44s
AMD64 Conda Python 3.11 Without Pandas	3m 39s
	50m 55s

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