[json] improve output to get leak_to and better logging.

recipe_modules/json/example.expected/basic.json

 [
   {
     "cmd": [
       "echo",
       "[1, 2, 3]"
     ],
     "name": "echo1",
     "stdout": "/path/to/tmp/json",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@[@@@",
@@ skipping 86 matching lines @@
     "name": "read json from file we just wrote",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"x\": 1, @@@",
       "@@@STEP_LOG_LINE@json.output@  \"y\": 2@@@",
       "@@@STEP_LOG_LINE@json.output@}@@@",
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
   {
+    "cmd": [
+      "python",
+      "cool_script.py",
+      "[TMP_BASE]/leak.json"
+    ],
+    "name": "leaking json",
+    "~followup_annotations": [
+      "@@@STEP_LOG_LINE@json.output@{@@@",
+      "@@@STEP_LOG_LINE@json.output@  \"x\": 1, @@@",
+      "@@@STEP_LOG_LINE@json.output@  \"y\": 2@@@",
+      "@@@STEP_LOG_LINE@json.output@}@@@",
+      "@@@STEP_LOG_END@json.output@@@"
+    ]
+  },
+  {
+    "cmd": [
+      "python",
+      "garbage.py",
+      "/path/to/tmp/json"
+    ],
+    "name": "invalid json",
+    "~followup_annotations": [
+      "@@@STEP_LOG_LINE@json.output (invalid)@here is some total@@@",
+      "@@@STEP_LOG_LINE@json.output (invalid)@garbage@@@",
+      "@@@STEP_LOG_END@json.output (invalid)@@@"
+    ]
+  },
+  {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]