Clusterfuzz

- Restructured internal imports to make pip package cleaner.
- AFL++ support.
- Many bug fixes.

- Various improvements for libClusterFuzz.
- Local development improvements.
- Add AFL support to the fuzzing engine pipeline.
- Various bug fixes.

- Improved ML-based fuzzing.
- Various bug fixes.

- Replaced webapp2 usage with Flask.
- Improved Syzkaller support.
- Added support for generic blackbox fuzzers.
- Removed remaining Python 2 compatibility code.
- Various bug fixes.

- Jobs page is now paginated.
- Next version requires new DB migrations due to addition of search keywords in Jobs.
- To perform migrations, please use:

python butler.py run -c path/to/config --non-dry-run migration.jobs_keywords

- Jobs page now has the ability to specify Fuzzer-Job mappings.
- Past crash regressions are now stored in the corpus backup.
- Set handle_<signal>=2 by default for sanitizer options in engine jobs.
- Fix local GCS issues.
- Remove more Python 2 support.
- Various bug fixes.

- Improved Syzkaller support.
- Support narrower bisection for regression/fix ranges.
- Improve Rust crash detection signatures.
- Improved Android KASan support.
- Batch datastore operations more aggressively.
- Improved grouping of crashes involving inline frames.
- Enable entropic fuzzing strategy in libFuzzer.
- Test past crash regressions in corpus pruning task.
- Various bug fixes.