Re-enable e2e tests

[anmazzotti]

The e2e workflow has been disabled after the discontinuation of OBS chart build for PRs.
It was refactored to build the chart "locally" on the GitHub Actions runner, however it ended up failing consistently on a few tests due to race condition.

The LOCAL_BUILD=true make e2e-tests action works when running on my workstation.

I think we should take the chance to refactor these tests, either to run them as integration tests instead, or to refactor them together with the elemental e2e tests. I also wonder if anything is already redundant considering the latter.