MM-13207 Add customizable timeout for link metadata and improve caching of errors (#10188)

* MM-13207 Add customizable timeout for link metadata and improve caching of errors

* Rename LinkMetadataTimeout to LinkMetadataTimeoutMilliseconds

* Add diagnostics for LinkMetadataTimeoutMilliseconds

config/default.json

@@ -358,7 +358,8 @@
     "ExperimentalSettings": {
         "ClientSideCertEnable": false,
         "ClientSideCertCheck": "secondary",
-        "EnablePostMetadata": false
+        "EnablePostMetadata": false,
+        "LinkMetadataTimeoutMilliseconds": 5000
     },
     "AnalyticsSettings": {
         "MaxUsersForStatistics": 2500
@@ -417,4 +418,4 @@
         "RemoteImageProxyURL": "",
         "RemoteImageProxyOptions": ""
     }
-}
+}