Record a removal's outcome, publish it, and read one directory once

The record kept only the intent, so a failed unlink read as removed; each
link now gets a synced intent and outcome line, and the outcome is the
module's link.removal event so it is not only a file on one machine.
The put-back hint no longer advises a symlink, an aliased directory is
read once, a machine-wide removal from user scope is said, and the state
directory names no owner a machine without an account cannot resolve.

modules/systemd/module.json

@@ -25,6 +25,9 @@
       ]
     }
   ],
+  "emits": [
+    "link.removal"
+  ],
   "build": {
     "artifacts": [
       {
@@ -53,7 +56,6 @@
       "id": "state",
       "type": "directory",
       "mode": "0700",
-      "owner": "${machine:account}",
       "place": "."
     }
   ]