Fix MultiscaleImage.read_spatial_region full region read #766

Job	Run time
SO copying (docker) TILEDB_EXISTS: no TILEDBSOMA_EXISTS: no	5m 51s
setuptools (ubuntu-22.04)	6m 14s
Wheel from sdist (ubuntu-22.04)	5m 13s
SO copying (docker) TILEDB_EXISTS: yes TILEDBSOMA_EXISTS: no	5m 36s
SO copying (macos) TILEDB_EXISTS: no TILEDBSOMA_EXISTS: no	7m 49s
setuptools (macos-12)	8m 11s
Wheel from sdist (macos-12)	7m 40s
SO copying (docker) TILEDB_EXISTS: yes TILEDBSOMA_EXISTS: yes	5m 39s
SO copying (macos) TILEDB_EXISTS: yes TILEDBSOMA_EXISTS: no	8m 40s
SO copying (macos) TILEDB_EXISTS: yes TILEDBSOMA_EXISTS: yes	10m 14s
	1h 11m 7s

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