Extract adders updates

[aletempiac]

This PR includes:

• Adding tests for decompose_multioutput util
• Fixes in decompose_multioutput util
• Experiment for extract_adder
• Comments in block_network to help the user understanding how HAs and FAs are created

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (1134d1d) 83.68% compared to head (4fdb61d) 83.59%.

Files	Patch %	Lines
.../algorithms/experimental/decompose_multioutput.hpp	75.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #631      +/-   ##
==========================================
- Coverage   83.68%   83.59%   -0.09%     
==========================================
  Files         186      187       +1     
  Lines       29617    29740     +123     
==========================================
+ Hits        24784    24862      +78     
- Misses       4833     4878      +45     

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