I've noticed that https://scan.coverity.com/projects/redis already
exists, but appears to be only updated on an ad-hoc basis. creating
[redis-unstable](https://scan.coverity.com/projects/redis-unstable?tab=project_settings)
project in coverity for this CI.
This PR adds a GitHub Action-based CI job to create a new Coverity build
once daily, so that there is always a recent scan available.
This is within the limit, as Redis is ~150K LOC and per
https://scan.coverity.com/faq#frequency :
> Up to 21 builds per week, with a maximum of 3 builds per day, for
projects with 100K to 500K lines of code
Before this is merged in, two new secrets will need to be created:
COVERITY_SCAN_EMAIL with the email address used for accessing Coverity
COVERITY_SCAN_TOKEN with the Project token from
https://scan.coverity.com/projects/redis-unstable?tab=project_settings
---------
Co-authored-by: Oran Agra <oran@redislabs.com>
