ENH: Add 2D cropping support and origin/spacing processing to ITK image readers

[joeykleingers]

Summary

Enhances ITK image reading filters with 2D-aware cropping capabilities and configurable origin/spacing processing timing, providing more flexible image import workflows.

Key Changes

CropGeometryParameter Enhancement

• Added is_2d flag to CropGeometryParameter to support 2D image cropping
• Enables proper cropping of 2D images without Z-axis constraints

ITKImageReader & ITKImportImageStack Improvements

• Added cropping options: Both filters now support voxel-based and physical subvolume cropping during image import
• Origin & Spacing Processing parameter: New parameter controls whether user-specified origin/spacing values are applied before (preprocessed) or after (postprocessed) image reading and cropping
  • Preprocessed: Origin/spacing applied before cropping (affects crop bounds interpretation)
  • Postprocessed: Origin/spacing applied after cropping (simpler workflow)
• Updated ReadImageUtils to handle cropping and origin/spacing processing timing

Testing

• Completely rewrote ITKImageReaderTest and ITKImportImageStackTest to comprehensively test all code paths and feature interactions
• Tests now validate all combinations of cropping, origin/spacing override, data type conversion, and processing timing

Testing Performed

• All new test cases pass with exemplar validation
• Tested 2D and 3D image cropping scenarios
• Verified origin/spacing processing in both pre and post modes
• Validated data type conversions with cropping

NOTE

This PR goes hand in hand with #1030 and should be approved and merged with it.