Arrabiata: remove old gadgets

[dannywillems]

These are leftovers from the initial draft of Arrabiata. The gadgets won't be used.
If we want to get them back, we can always revert the commit. But for now, I would remove them to clean the code.

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 72.42%. Comparing base (653dbc2) to head (d13ecf4).
Report is 23 commits behind head on master.

Files with missing lines	Patch %	Lines
arrabiata/src/columns.rs	0.00%	1 Missing ⚠️
arrabiata/src/witness.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2698      +/-   ##
==========================================
- Coverage   72.52%   72.42%   -0.10%     
==========================================
  Files         246      246              
  Lines       58241    58055     -186     
==========================================
- Hits        42238    42046     -192     
- Misses      16003    16009       +6     

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