[Key Connector] Test that Key Connector URL can be reached before saving (#1291)

* Test that Key Connector URL can be reached before saving

* Update jslib

* Add styling to validation messages

* Use inline button, fix styling

* Add accessibility call out to form validation

src/locales/en/messages.json

@@ -4571,5 +4571,14 @@
   },
   "migratedKeyConnector": {
     "message": "Migrated to Key Connector"
+  },
+  "keyConnectorTest": {
+    "message": "Test"
+  },
+  "keyConnectorTestSuccess": {
+    "message": "Success! Key Connector reached."
+  },
+  "keyConnectorTestFail": {
+    "message": "Cannot reach Key Connector. Check URL."
   }
 }