COMP: Include itkImageRegionIteratorWithIndex.h where the type is used

[hjmjohnson]

Add the missing #include "itkImageRegionIteratorWithIndex.h" to the two files that use the type. Without it this module does not compile against current ITK main — 8 translation units fail.

Why it broke

Both files use ImageRegionIteratorWithIndex but never include its header, relying on it arriving transitively through another ITK header. Current ITK no longer provides it that way.

The two files fail differently because of how the name is spelled:

File	Spelling	Compiler behaviour
include/itkCannyEdgeDetectionRecursiveGaussianImageFilter.hxx:411	unqualified (inside namespace itk)	error: use of undeclared identifier 'ImageRegionIteratorWithIndex', then cascading errors on uit
test/itkRegionCompetitionImageFilterTest1.cxx:117	itk::-qualified	error: no template named 'ImageRegionIteratorWithIndex' in namespace 'itk' — the compiler then recovers by substituting ImageRegionConstIteratorWithIndex, which rejects the later itr.Set(...) calls

The second case is worth noting: the reported errors are no member named 'Set' in 'itk::ImageRegionConstIteratorWithIndex<...>', which reads like a wrong-iterator-type bug. It is not — the declaration at line 117 already asks for the non-const iterator. It is the same missing include, seen through the compiler's error recovery.

These are the only two files in the module that use the type without including its header.

Verification

Built as an ITK remote module (-DModule_LesionSizingToolkit=ON), Release, AppleClang, arm64, macOS 26.5 SDK, against ITK main at 4213421.

Target	Before	After
LesionSizingToolkitTestDriver	8 failing TUs	0
LesionSizingToolkit-all	10 failing targets	0, exit 0

Failing translation units before the fix:

itkCannyEdgesDistanceAdvectionFieldFeatureGeneratorTest1.cxx
itkCannyEdgesDistanceFeatureGeneratorTest1.cxx
itkCannyEdgesFeatureGeneratorTest1.cxx
itkLesionSegmentationMethodTest4.cxx
itkLesionSegmentationMethodTest8.cxx
itkLesionSegmentationMethodTest8b.cxx
itkMinimumFeatureAggregatorTest1.cxx
itkRegionCompetitionImageFilterTest1.cxx

The breakage is not new to any recent change here — building the previously ITK-pinned commit (affbf7b095…) against the same ITK reproduces the identical 8 failures, so it has been latent since ITK stopped providing the header transitively.

Not covered: the test suite was not executed (requires the module's test data); this change is verified at compile/link only.

[hjmjohnson]

Missing includes (previoiusly transitively included).