fix: preserve stringdtype in zarr v3 round trips #21439

Job	Run time
detect ci trigger	12s
Event File	7s
cache-pixi-lock	10s
ubuntu-latest \| test-py311-min-versions	10m 24s
windows-latest \| test-py314	11m 48s
ubuntu-latest \| test-py311	10m 58s
ubuntu-latest \| test-py311-bare-min-and-scipy	2m 17s
ubuntu-latest \| test-py314-no-numba	6m 44s
ubuntu-latest \| test-py314 (flaky)	1m 40s
macos-latest \| test-py314	9m 55s
windows-latest \| test-py311	19m 11s
macos-latest \| test-py311	10m 42s
ubuntu-latest \| test-py314-with-typing	16m 27s
ubuntu-latest \| test-py314	6m 56s
ubuntu-latest \| test-py314-no-dask	3m 52s
ubuntu-latest \| test-py311-bare-minimum	2m 47s
ubuntu-latest \| test-py311-with-typing (mypy)	3m 31s
	1h 57m 41s

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