Apart from running CIFuzz for each relevant PR, let's run it unconditionally for each push to master to detect possible issues (caused by ignored PRs, etc.). Followup to 94f660a8fe.
94f660a8fe
Fuzz only PRs with relevant changes (source code and fuzzer corpora) to save resources.
Per-PR fuzzing provided by OSS-Fuzz using GH workflows. See: https://google.github.io/oss-fuzz/getting-started/continuous-integration/