enable simulation of controlled gates in classical simulator

[GregDMeyer]

Currently, only X, CNOT, TOFFOLI, SWAP, and measurement are supported by cirq.ClassicalStateSimulator. This pull request adds support for versions of the first four gates with an arbitrary number of controls (as generated by the .controlled() function).

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 97.81%. Comparing base (f246c2b) to head (083f79c). Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6589   +/-   ##
=======================================
  Coverage   97.81%   97.81%           
=======================================
  Files        1063     1063           
  Lines       91761    91796   +35     
=======================================
+ Hits        89755    89793   +38     
+ Misses       2006     2003    -3     

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[GregDMeyer]

whoops, I realized why I wasn't seeing the linter errors locally---I was mistaken about what running format-incremental checked for. I thought it was equivalent to pylint but only on changed lines. Anyway all pylint checks seem to pass with my latest commit so I think CI should pass now :-)