Switch to Pyrefly for type checking instead of mypy

[mhucka]

Is your feature request related to a use case or problem?

A number of other projects are switching from mypy to Pyrefly for type checking Python code. We should do the same for Quantumlib projects if possible. Pyrefly is much faster than mypy and has better IDE support.

What solution or approach do you envision?

1. Use Pyrefly's facility for creating a configuration based on an existing mypy configuration
2. Run Pyrefly to find and fix whatever problems it flags
3. Add a Pyrefly hook configuration to .pre-commit-config.yaml
4. Replace the type check in CI with a Pyrefly-based one

How urgent is this for you?

P2 – needed within two quarters

[rosspeili]

@mhucka when @pavoljuhas is back, and if you guys agree, I can pick this both for Cirq and OpenFermion.

[mhucka]

@rosspeili Pyrefly is a "go". Thanks for volunteering!

[rosspeili]

Thanks @mhucka, I will start with OpenFermion, and if you like the approach, feel free to assign the relevant Cirq issue as well. 🙏

[pavoljuhas]

@rosspeili - if possible, please use ASCII characters instead of ツンデレ as your author name in git commits, which will make them easier to find in git logs.

[rosspeili]

Hey @pavoljuhas added the username as prefix. Hope this works better. <3

[rosspeili]

Migration pr is in #1433, and CI looks green. Lmk how this looks @mhucka / @pavoljuhas and if I am missing something. Thanks <3