API design: Add critical policy and resolution data to device health API (#18715)

Fresh PR to avoid product design PRs messing with the PR open time KPI
(original: https://github.com/fleetdm/fleet/pull/16982)

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Co-authored-by: Noah Talerman <47070608+noahtalerman@users.noreply.github.com>

docs/REST API/rest-api.md

@@ -3258,10 +3258,14 @@ This report includes a subset of host vitals, and simplified policy and vulnerab
     "updated_at": "2023-09-16T18:52:19Z",
     "os_version": "CentOS Linux 8.3.2011",
     "disk_encryption_enabled": true,
+    "failing_policies_count": 1,
+    "failing_critical_policies_count": 1, // Fleet Premium only
     "failing_policies": [
       {
         "id": 123,
         "name": "Google Chrome is up to date",
+        "critical": true, // Fleet Premium only
+        "resolution": "Follow the Update Google Chrome instructions here: https://support.google.com/chrome/answer/95414?sjid=6534253818042437614-NA"
       }
     ],
     "vulnerable_software": [