[WIP] STY: Update filter code to implement a standard naming convention

[imikejackson]

Using claude-code to update filter source codes to use a more consistent naming convention which should more closely match the clang-tidy file but also become easier to read.

Rules such as:
pointer variables should have Ptr suffix
reference variables should have Ref suffix
Variables that point to or reference a Geometry type should end with Geom
When looping over every element in an ImageGeometry, we should be using "TotalVoxels" and "voxelIdx" instead of i in those loops.

Will update with more rules as they are implemented.