ci: run integration tests on main and schedule

[efiop]

Right now we only run tests on PRs, but it is useful to also run them on main and on schedule, so internal and external contributors could have a frame of reference for their changes and general health of the project (e.g. some 3rd party dependency updated and broke something or our service broke over the weekend/night etc).

Note that at any given moment there will only be 1 worker running integration tests for commits from main, so we shouldn't waste much resources even during fast merge pace.

[efiop]

@chamini2 Great question! Thought about creating a slack alert (might do after this), but at the very least I will be keeping an eye while I'm doing stuff around this project and will make sure to fix (or ping the author of PR that broke it if I can't) or escalate if the problem is external. It is in my interest as a contributor. 🙂

[squat]

I like this and enable that by default on my pubic repos. Normally I put the workflow badge on the readme so u can see when it's busted. We could also set the notification email to our mailing list so we all get notified