We're running against the usage limits in Gitlab CI (500), and Github
Actions should have more (2000).
So this patch replaces Gitlab CI with Github actions for running
integration tests, and build and push Docker images (to Dockerhub and
Gitlab registry).
We'll see how the usage levels are in a few months.
govulncheck will complain when run on older Go versions that are known
to have security issues. Github setup-go action has a cache for the
"latest" go version and sometimes the latest isn't really used.
So sometimes, this generates false positives because govulncheck is run
on an older Go version, which is not a problem in chasquid itself.
To prevent those false positives, this patch asks the Github CI to
always check for the latest Go version when running govulncheck.
