feat(ci): switch to GH action for testing CI build image

[hainenber]

PR Description

From what I've checked, drone.io's configuration no longer supports triggering builds based on changed paths. We should switch to GitHub Actions for this feature.

There should be no risks as the migrated parts are only for building throw-away test images, no pushing to any remote registry.

Which issue(s) this PR fixes

Notes to the Reviewer

PR Checklist

• CHANGELOG.md updated

[tpaschalis]

Thanks for opening that PR! Even though Drone itself does not support paths for its trigger syntax, there are third-party extensions that can be used for this.

For this reason, and since I think it has been working fine, I think it's best we continue using Drone for the build-image CI step. WDYT?

[hainenber]

Yes, I noticed there's a 3rd-party extension that would help our issue atm but as far as I'm aware, this would require the infrastructure complexity of hosting said extension as well as secrets handling/storage to connect Drone endpoint with it.

If we migrate to GH Actions, it'd be a hassle-(free) :)

[rfratto]

For security reasons, we're currently unable to use Drone on PRs, and can only do it after merge. Given that, I think it makes sense to test the CI build images using GitHub Actions, so that we have validations earlier.

cc @tpaschalis WDYT?

[tpaschalis]

cc @tpaschalis WDYT?

Yeah, I'm okay with it (sorry missed your previous message @hainenber)

[rfratto]

Thanks @hainenber! I'm going to clean this PR up a little bit (to remove your test changes and resign the Drone config) and then get this merged. Nice work!