[dagit] Add ID field to DaemonHealth
Summary: I noticed an Apollo cache warning on daemonHealth. Adding an id field to DaemonStatus should help out.
Test Plan: View /instance, reload the page with daemons on and off. Verify that caching is correct and that there are no Apollo warnings.
Reviewers: johann, prha, dgibson
Reviewed By: dgibson
Differential Revision: https://dagster.phacility.com/D6357