ENH: Add 20 CID blobs for ITKSphinxExamples Core/Common visuals

[hjmjohnson]

Add 20 CID/ blobs: recreated conceptual visuals for ITKSphinxExamples src/Core/Common/ examples whose original binaries from ITKSphinxExamples#440 were never published and are unrecoverable. Referenced by InsightSoftwareConsortium/ITKSphinxExamples#455.

Review gallery — all 20 recreated figures

ApplyAFilterOnlyToASpecifiedRegionOfAnImage/Relationship.png

ApplyCustomOperationToEachPixelInImage/Operation.png

ApplyCustomOperationToEachPixelInImage/Relationship.png

BoundingBoxOfAPointSet/BoundingBox.png

BresenhamLine/Operation.png

BresenhamLine/Segmentation.png

ConvertArrayToImage/Relationship.png

ConvertArrayToImage/Sphere.png

ConvertArrayToImage/Sphere3D.png

CreateDerivativeKernel/DerivativeKernel.png

CreateDerivativeKernel/DerivativeOperator.png

CreateGaussianKernel/GaussianBlur.png

CreateGaussianKernel/GaussianKernel.png

CreateVectorImage/Operation.png

CropImageBySpecifyingRegion/3DVolume.png

CropImageBySpecifyingRegion/ExtractedSlice.png

ImageRegionIntersection/ImageRegionIntersection.png

MakePartOfImageTransparent/Transparency.png

MiniPipeline/MiniPipeline.png

ReadAPointSet/tetrahedron.png

[hjmjohnson]

Extended scope: also mirrors the 6 ComputeFFTInOneDimension SHA512 blobs from data.kitware.com (the only host that still serves them; itk.org and this repo 404). All hashes verified on download. This makes #63 carry all data ITKSphinxExamples CI currently fails to fetch.

[hjmjohnson]

Scope reverted to the 20 visual CIDs only — the 6 FFT SHA512 blobs moved to their own PR, #64.