Move to method dispatch using act_on for CliffordState, Tableau and ChForm

[smitsanghavi]

Delete all the now-unneeded methods.

Remaining work: refactor the measurement code

#2948 #2423

[balopat]

it seems that we could just import the types from these packages in cirq.sim.clifford.__init__.py and then use them directly. It is the more typical style in Cirq allowing for shorter names and easier code completion. Then you can do from cirq.sim import clifford as clifford and clifford.ActOn...

[smitsanghavi]

You're right, and the style guide agrees with you https://cirq.readthedocs.io/en/latest/docs/dev/style.html.

But I feel I have seen the reverse pattern being followed, the most specific subpaths are imported instead of the top-level module (except in tests where it's cirq.Whatever). But I'll at least fix the clifford stuff for this PR to follow the style guide.

[smitsanghavi]

Had to shuffle the clifford.__init__.py to avoid circular dependencies. Since these all classes are very closely intertwined, there is a high chance of circular dependencies if using cirq.sim.clifford directly.

[balopat]

Yeah now that happens. The init module orderings is a dark art.