Move the self-check out of the controller into mesh-self-check, so its runs and findings no longer need the controller's lease (issue 1952)

The probes whose facts are on the bus run with their assertions unchanged (D6, D7, D15, DW, H-bus); the rest answer deferred, naming what they lack, never a pass. Findings go to its own bucket for the condition keeper; each run is kept a week and said as checked. The finding layout is a copy of mesh-sdk's S3 until that lands.

modules/mesh-self-check/module.json

@@ -0,0 +1,67 @@
+{
+  "module": "mesh-self-check",
+  "version": "1",
+  "runs-as": "mesh-self-check",
+  "claims": [
+    {
+      "name": "mesh-self-check",
+      "scope": "mesh",
+      "serves": [
+        "doctor",
+        "probes"
+      ]
+    }
+  ],
+  "emits": [
+    "checked"
+  ],
+  "invokes": [
+    "nats.nats_streams",
+    "nats.nats_closed_connections",
+    "seat:mesh-watchdogs.signals"
+  ],
+  "state": [
+    "findings",
+    "verdict",
+    {
+      "name": "verdicts",
+      "ttl-seconds": 604800
+    }
+  ],
+  "own-secrets": {
+    "broker": "${dir:state}/broker"
+  },
+  "secrets-owner": "mesh-self-check",
+  "resources": [
+    {
+      "id": "account",
+      "type": "user",
+      "name": "mesh-self-check",
+      "shell": "/usr/bin/nologin",
+      "home": "/var/lib/mesh-self-check"
+    },
+    {
+      "id": "state",
+      "type": "directory",
+      "mode": "0700",
+      "owner": "mesh-self-check",
+      "place": ".",
+      "unknown": "program"
+    }
+  ],
+  "build": {
+    "artifacts": [
+      {
+        "name": "tools",
+        "kind": "bundle",
+        "language": "go",
+        "system": "arch",
+        "from": "cmd/mesh-self-check",
+        "binary": "mesh-self-check",
+        "loads": [
+          "mesh-self-check"
+        ]
+      }
+    ]
+  }
+}