docker: trust the mesh's registry from the runtime's own module (hq issue 190)

The controller's private network writes insecure-registries into daemon.json, a file this
module owns. The runtime's module states it instead, through ${seat:mesh-artifact-store:reach}
(hq ADR 0222), so the controller can stop generating its registry-trust resources.

modules/docker/module.json

@@ -56,7 +56,7 @@
       "path": "/etc/docker/daemon.json",
       "mode": "0644",
       "into": "json",
-      "content": "{\"live-restore\": true}\n"
+      "content": "{\"live-restore\": true, \"insecure-registries\": [\"${seat:mesh-artifact-store:reach}\"]}\n"
     },
     {
       "id": "runtime",