Measure density matrix inplace

[GiggleLiu]

Fix #531

• Measure density matrix inplace, support reset and remove post-processing.
• Measure operators on density matrix.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.73%. Comparing base (3c6a767) to head (546a45f).
Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #532      +/-   ##
==========================================
- Coverage   87.08%   86.73%   -0.35%     
==========================================
  Files          24       13      -11     
  Lines        1502      867     -635     
==========================================
- Hits         1308      752     -556     
+ Misses        194      115      -79     

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[GiggleLiu]

@Roger-luo It is ready for review. BTW, what is CI-MISC? Is it safe to remove it?

[Roger-luo]

BTW, what is CI-MISC? Is it safe to remove it?

MISC is nightly and other non-LTS versions.