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.

Partially implements #7515

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.27%. Comparing base (f7a90c2) to head (31f8647).
⚠️ Report is 96 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7625      +/-   ##
==========================================
- Coverage   97.50%   97.27%   -0.23%     
==========================================
  Files        1103     1105       +2     
  Lines       99665   102155    +2490     
==========================================
+ Hits        97179    99375    +2196     
- Misses       2486     2780     +294     

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[pavoljuhas]

LGTM, thank you for setting this up.

[ToastCheng]

Hi @pavoljuhas! From my local test, the project name needs to be in lowercase, since it's used as a Docker image name, which has a lowercase restriction. I also updated my OSS-Fuzz commit accordingly, sorry about the confusion!

(running on OSS-Fuzz repo root)
python infra/helper.py shell Cirq
INFO:__main__:Running: docker build -t gcr.io/oss-fuzz/Cirq --file /usr/local/google/home/toastcheng/dev/qc/oss-fuzz/projects/Cirq/Dockerfile /usr/local/google/home/toastcheng/dev/qc/oss-fuzz/projects/Cirq.
[+] Building 0.0s (0/0)                                                                                                                                                                          docker:default
ERROR: failed to build: invalid tag "gcr.io/oss-fuzz/Cirq": repository name must be lowercase
ERROR:__main__:Docker build failed.

Note: this command is from OSS-Fuzz debugging doc