PR CI should run using `docker` for testcontainers

[andrewazores]

See #949
See #952
See #955
See #759

And most of all see #767

PR CI currently runs very simply and directly using mvn verify and podman available in the runner. CI on main uses a different workflow which is broken into more stages and runs the integration tests under docker, to avoid a testcontainers issue where starting additional containers under podman fails (for unknown, difficult to diagnose and locally irreproducible reasons). This would allow the new batch of Agent integration tests to run during CI, not just after merge.