Add a flag to the Firebase Sessions test app for verbose Sessions (#7004)

Author: tejasd

firebase-sessions/test-app/src/main/AndroidManifest.xml

@@ -43,6 +43,11 @@
       android:process=":second"
       android:theme="@style/Theme.Widget_test_app.NoActionBar" />
 
+    <!-- Override value to 1.0 to always have a fireperf verbose session -->
+    <meta-data
+        android:name="sessions_sampling_percentage"
+        android:value="0.01" />
+
     <meta-data
       android:name="firebase_performance_logcat_enabled"
       android:value="true" />