Add observer type to Perf event

Summary: While looking at the event stream it is useful to know which observer type fired it

Reviewed By: lblasa

Differential Revision: D39430756

fbshipit-source-id: bc52f085a5497692f8076b12a9c015cc33a19d1e

desktop/plugins/public/ui-debugger/components/main.tsx

@@ -58,6 +58,10 @@ export const columns: DataTableColumn<PerfStatsEvent>[] = [
     key: 'txId',
     title: 'TXID',
   },
+  {
+    key: 'observerType',
+    title: 'Type',
+  },
   {
     key: 'nodesCount',
     title: 'Total nodes',