feat(ui): show the number of hidden label on the overview modal

We only render top 9 labels, add a counter showing how many were skipped

ui/src/Components/OverviewModal/OverviewModalContent.test.js

@@ -37,6 +37,17 @@ describe("<OverviewModalContent />", () => {
           { value: "bar3", raw: "foo=bar3", hits: 4, percent: 25, offset: 75 }
         ]
       },
+      {
+        name: "bar",
+        hits: 20,
+        values: Array.from(Array(20).keys()).map(i => ({
+          value: `baz${i + 1}`,
+          raw: `bar=baz${i + 1}`,
+          hits: 1,
+          percent: 5,
+          offset: i * 5
+        }))
+      },
       {
         name: "alertname",
         hits: 5,