Add code required by sum-of-squares circuits over images

[loreloc]

As per title.

Closes #281 .

[codecov]

Codecov Report

Attention: Patch coverage is 19.09091% with 178 lines in your changes missing coverage. Please review.

Project coverage is 68.17%. Comparing base (6d5b578) to head (dcf9252).
Report is 12 commits behind head on main.

Files with missing lines	Patch %	Lines
cirkit/templates/circuit_templates/utils.py	0.00%	96 Missing ⚠️
cirkit/backend/torch/layers/input.py	38.88%	22 Missing ⚠️
cirkit/symbolic/operators.py	37.14%	22 Missing ⚠️
cirkit/symbolic/layers.py	36.66%	19 Missing ⚠️
cirkit/templates/circuit_templates/data.py	0.00%	15 Missing ⚠️
cirkit/backend/torch/rules/layers.py	60.00%	2 Missing ⚠️
cirkit/templates/circuit_templates/__init__.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #284      +/-   ##
==========================================
- Coverage   69.20%   68.17%   -1.03%     
==========================================
  Files          52       52              
  Lines        5367     5473     +106     
  Branches      598      616      +18     
==========================================
+ Hits         3714     3731      +17     
- Misses       1436     1526      +90     
+ Partials      217      216       -1     

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