Fix tutorials after introduction of MetricFetchResult (#1243)

Summary:
X-link: facebook/Ax#1243

Pull Request resolved: #1475

A few tutorials were not compatible with the new way we fetch data. In this diff we change custom metrics to return Ok(data) instead of data, and change `trial.fetch_data()` => `Metric._unwrap_trial_data_multi(results=trial.fetch_data())`.

In the future we may want to add some copy in the tutorials discussing Result, but we should land this for now to get things working again ASAP

Reviewed By: dme65

Differential Revision: D40994060

fbshipit-source-id: 9a5f86273a7da8496e480a0d7ca0aa2c03ecb194

Author: mpolson64

tutorials/custom_botorch_model_in_ax.ipynb

@@ -1085,6 +1085,7 @@
     "    Runner,\n",
     "    SearchSpace,\n",
     ")\n",
+    "from ax.utils.common.result import Ok\n",
     "from botorch.test_functions import Branin\n",
     "\n",
     "\n",
@@ -1106,7 +1107,7 @@
     "                    \"sem\": float(\"nan\"),  # SEM (observation noise) - NaN indicates unknown\n",
     "                }\n",
     "            )\n",
-    "        return Data(df=pd.DataFrame.from_records(records))\n",
+    "        return Ok(value=Data(df=pd.DataFrame.from_records(records)))\n",
     "\n",
     "\n",
     "# Search space defines the parameters, their types, and acceptable values.\n",