Adding qulacs to extra

[scarrazza]

Closes #1409.

Checklist:

• Reviewers confirm new code works as expected.
• Tests are passing.
• Coverage does not decrease.
• Documentation is updated.

[alecandido]

Yes, it should have been an extra from the beginning, sorry.

[alecandido]

Apparently, tests are randomly failing (they were all because of numerical values). I'm rerunning them, but that's an issue on its own.
https://github.com/qiboteam/qibo/actions/runs/10226346562/attempts/1?pr=1410

[scarrazza]

I think this is due to the torch version update. If I don't update the lock file, tests are passing: https://github.com/qiboteam/qibo/actions/runs/10226488301. I will probably revert the torch update.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.94%. Comparing base (64d78bc) to head (9f1f3dd).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1410   +/-   ##
=======================================
  Coverage   99.94%   99.94%           
=======================================
  Files          78       78           
  Lines       11222    11222           
=======================================
  Hits        11216    11216           
  Misses          6        6           

Flag	Coverage Δ
unittests	99.94% <ø> (ø)

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