Previously, the `aio_monitoring` job was testing both the stable
(https://angular.io/) and the @next (https://next.angular.io/) versions.
This commit splits the tests into two separate jobs (still run as part
of the same workflow). This speeds up the tests (since the two jobs can
now run in parallel) and makes it easier to isolate failures (e.g.
identify which branch is failing, disable one of the two, etc.).
(Credits to @petebacondarwin 😉)
PR Close#30110
582ef2e7b4