Fix no message for zero trackers

Bug: Tracker Status UI: No Message for Zero Trackers.

The TrackerStatus function computes totalTrackersPillText for the
zero-trackers case but never displays it. When totalTrackersBlocked ===
0, the condition {totalTrackersBlocked > 0 && <TickPill .../>} prevents
rendering any tracker status message. The legacy TrackerStatusLegacy
displays "No trackers blocked" or "No trackers found" in this scenario,
but the new implementation shows nothing, breaking the expected UI
behavior for sites with no blocked trackers.

#2039 (comment)

Author: jsoningram

special-pages/pages/new-tab/app/activity/integration-tests/activity.spec.js

@@ -159,6 +159,14 @@ test.describe('activity widget', () => {
         await ap.didRender();
         await ap.hidesCookiePopupIndicatorWhenNotBlocked();
     });
+    test('shows zero-tracker messages with new component when CPM enabled', async ({ page }, workerInfo) => {
+        const ntp = NewtabPage.create(page, workerInfo);
+        const ap = new ActivityPage(page, ntp);
+        await ntp.reducedMotion();
+        await ntp.openPage({ additional: { ...defaultPageParams, cpm: 'true' } });
+        await ap.didRender();
+        await ap.showsZeroTrackerMessagesWithCpm();
+    });
     test('after rendering and navigating to a new tab, data is re-requested on return', async ({ page }, workerInfo) => {
         const ntp = NewtabPage.create(page, workerInfo);
         const ap = new ActivityPage(page, ntp);