fix: add for-loop elements to UnsupportedElementSwapper and add warning messages (issue #4716)

[mkforsb]

This adds CtFor and CtForEach to the set of elements swapped out by spoon-smpl's UnsupportedElementSwapper along with a warning log message for each replaced element.

Should be a slight improvement on the current user experience (see #4716).

[monperrus]

@mkforsb Would we able to add a test case to specify this behavior?

[mkforsb]

@mkforsb Would we able to add a test case to specify this behavior?

Two simple tests added.

[MartinWitt]

Could you document the current implementation state inside the subproject? Missing elements are a factory when you choose your tool, and we should be as honest as possible about the limitations.

[monperrus]

@MartinWitt the reference doc is Mikael Forsberg's master's thesis "Design and Implementation of Semantic Patch Support for the Spoon Java Transformation Engine' at KTH Royal Institute of Technology".