enable CodeQL checks

[mythi]

This PR is a reference for few improvements in our repositories

1. enable dependabot github-actions updates using pinned versions (dependabot understands pinned versions nowadays). Pinned versions are considered safe since attackers could re-push tags. The move to pinned versions must be done manually.
2. enable CodeQL checks for our Go based code (to be checked: maintainers might have to enable this in the repo settings also)

Ref: confidential-containers/confidential-containers#46

[github-advanced-security]

This pull request sets up GitHub code scanning for this repository. Once the scans have completed and the checks have passed, the analysis results for this pull request branch will appear on this overview. Once you merge this pull request, the 'Security' tab will show more code scanning analysis results (for example, for the default branch). Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results. For more information about GitHub code scanning, check out the documentation.

[fitzthum]

LGTM. I guess this might create a bit more work for us tho. We'll see what the results are.

[mythi]

I did a test run in my fork and checked the results. It did not show up anything that would trigger any actions.

[mythi]

@bpradipt is this OK to merge?

[bpradipt]

@mythi missed this.. LGTM

[fitzthum]

CI is stuck 😞

[mythi]

CI is stuck 😞

@BbolroC @bpradipt do I need an ok-to-test label here?

[mythi]

This can be merged now. Some tests are failing but most likely not related to this PR.

[mythi]

I have two approvals and CI is green so merging.