Testing: Introduced continuous fuzzing

[AdamKorcz]

What this PR does / why we need it:
This PR introduces fuzzing for Loki. Fuzzing is a way of testing applications whereby pseudo-random data is passed to a target function with the goal of finding bugs and vulnerabilities. The fuzzer in this PR is implemented with the go-fuzz fuzzing engine.

I have worked on setting continuous fuzzing up for these two fuzzers which will allow them to run for longer and find harder-to-find bugs as well. I will shortly set up the integration for Loki on OSS-fuzz, and upon merging the fuzzer here, it will be able to run continuously through OSS-fuzz. OSS-fuzz is a free service for open source projects, and if/when bugs are found, maintainers get notified with an email containing a link to a detailed bug report with stacktrace and reproducer test-case. While it is a free service it is offered with an implied expectation that bugs are fixed, so that the resources spent on fuzzing Loki go towards resolving bugs in the codebase.

All that is needed to setup continuous fuzzing would be at least one maintainer email address.

For some examples of previous bugs found from fuzzing Golang projects I recommend checking out the trophy list on the go-fuzz repository: https://github.com/dvyukov/go-fuzz#trophies

[CLAassistant]

All committers have signed the CLA.

[AdamKorcz]

I have set up the integration for this fuzzer to be run continuously through OSS-fuzz here: google/oss-fuzz#4777

Once integrated, OSS-fuzz will run the fuzzer continuously and notify maintainers if bugs are found. Notifications will include detailed reports with reproducer-testcases and stacktraces. Maintainers also have access to statistics of fuzz runs and the effectiveness of the fuzzer (execution speed, OOM's, Timeouts etc).

[cyriltovena]

How do we get notified exactly ?

[AdamKorcz]

How do we get notified exactly ?

When a bug is found, an email is sent out to all maintainers with a link to the report. All previous reports are available when logging into the dashboard as well.

[cyriltovena]

LGTM Thanks you !

[AdamKorcz]

Perfect. As mentioned, to complete the integration on the OSS-fuzz side, at least one maintainers email address is needed in the project.yaml file over there. Would you be able to leave an email in a comment?