[Bug] Fix qubo tutorial, add tests for whitepaper snippets

[jpmoutinho]

Fixes the QUBO tutorial and adds tests replicating all the code snippets used in the Qadence whitepaper.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.45%. Comparing base (f5b5adb) to head (87c7db7).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #635      +/-   ##
==========================================
+ Coverage   85.20%   85.45%   +0.24%     
==========================================
  Files         193      194       +1     
  Lines       16369    16594     +225     
  Branches     1404     1406       +2     
==========================================
+ Hits        13948    14180     +232     
+ Misses       2017     2012       -5     
+ Partials      404      402       -2     

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