Default copy and move of iterators, using `ITK_DEFAULT_COPY_AND_MOVE`

[N-Dekker]

Replaced hand-written copy-constructors and assignment operators of four iterators with the equivalent ITK_DEFAULT_COPY_AND_MOVE macro calls.

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• Follow-up to pull request #4652

[N-Dekker]

I did look carefully at those hand-written copy-constructors and assignment operators to check that they really just do "the default thing". But honestly an extra glance wouldn't harm 😃

Note that some copy functions of other iterators seem to do non-default things, for example:

• the copy-constructor of ConstNeighborhoodIterator: https://github.com/InsightSoftwareConsortium/ITK/blob/efe3dce79945bd476ef3275e959c373d14e1090a/Modules/Core/Common/include/itkConstNeighborhoodIterator.hxx#L240
• the copy-constructor of ImageConstIteratorWithIndex: https://github.com/InsightSoftwareConsortium/ITK/blob/efe3dce79945bd476ef3275e959c373d14e1090a/Modules/Core/Common/include/itkImageConstIteratorWithIndex.hxx#L46

I did not include those seemingly non-default-behaving copy-functions with this pull request.