Add negativity to quantum_info.entanglement

[renatomello]

This needs to be merged after #1454

EDIT: Also needs #1462

Checklist:

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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.93%. Comparing base (9fb5161) to head (f5da5d8).
Report is 19 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1456   +/-   ##
=======================================
  Coverage   99.93%   99.93%           
=======================================
  Files          81       81           
  Lines       11750    11783   +33     
=======================================
+ Hits        11742    11775   +33     
  Misses          8        8           

Flag	Coverage Δ
unittests	99.93% <100.00%> (+<0.01%)	⬆️

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[renatomello]

@AlejandroSopena @BrunoLiegiBastonLiegi @stavros11 this is ready but pointing to the partial_transpose branch in PR #1462. That PR needs to be merged before this one.