Add cifuzz CI config for OSS-Fuzz

[ToastCheng]

After adding the Cirq to OSS-Fuzz project list, we'll need to configure GitHub action to run the CI fuzzer. This PR basically follows https://google.github.io/oss-fuzz/getting-started/continuous-integration/ to enable the workflow.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.50%. Comparing base (f7a90c2) to head (101586c).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7625   +/-   ##
=======================================
  Coverage   97.50%   97.50%           
=======================================
  Files        1103     1103           
  Lines       99665    99707   +42     
=======================================
+ Hits        97179    97222   +43     
+ Misses       2486     2485    -1     

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