Inconsistent handling when disable event-execution in multisite

Under a multisite, only the main site is checked to trigger the runner's backoff functionality, but each subsite can disable its execution independently. The runner's CLI commands respect the value for individual sites, but the runner's backoff isn't triggered by subsites.

Under multisite, either the option to disable automatic execution should be an instance-wide control (site option), or the runner should be updated to handle individual subsites differently than they are now. The `orchestrate runner-only get-info` command will likely need to be updated too.