[server] SN read quota versioned stats not initialized after restart

The currentVersion and backupVersion of ServerReadQuotaUsageStats are not
set after server restart because handleStoreChanged is invoked for all
stores when the store repo undergoing refresh before we initialize and
register store change listener in ReadQuotaEnforcementHandler (part
of the ListenerService). As a result metrics that depend on current
and backup versions will not show up properly until store is updated.

The fix is to during initialization of ReadQuotaEnforcementHandler we
will invoke handleStoreChanged for all stores after we register store
change listener.

The bug is actually reproducible in existing integration test. However,
it was not caught because the test was broken/misconfigured...

internal/venice-test-common/src/integrationTest/java/com/linkedin/venice/fastclient/FastClientIndividualFeatureConfigurationTest.java

@@ -186,6 +186,10 @@ public void testServerReadQuota() throws Exception {
       LOGGER.info("RESTARTING servers");
       veniceCluster.stopAndRestartVeniceServer(veniceServerWrapper.getPort());
     }
+    serverMetrics.clear();
+    for (int i = 0; i < veniceCluster.getVeniceServers().size(); i++) {
+      serverMetrics.add(veniceCluster.getVeniceServers().get(i).getMetricsRepository());
+    }
     for (int j = 0; j < 5; j++) {
       for (int i = 0; i < recordCnt; i++) {
         String key = keyPrefix + i;
@@ -198,7 +202,7 @@ public void testServerReadQuota() throws Exception {
       quotaRequestedQPSSum += serverMetric.getMetric(readQuotaRequestedQPSString).value();
       assertEquals(serverMetric.getMetric(readQuotaAllowedUnintentionally).value(), 0d);
     }
-    assertTrue(quotaRequestedQPSSum >= 0, "Quota request sum: " + quotaRequestedQPSSum);
+    assertTrue(quotaRequestedQPSSum > 0, "Quota request sum: " + quotaRequestedQPSSum);
   }
 
   @Test(timeOut = TIME_OUT)

services/venice-server/src/main/java/com/linkedin/venice/listener/ReadQuotaEnforcementHandler.java

@@ -173,6 +173,8 @@ public final void init() {
       for (Version version: versions) {
         customizedViewRepository.subscribeRoutingDataChange(version.kafkaTopicName(), this);
       }
+      // also invoke handle store change to ensure corresponding token bucket and stats are initialized.
+      handleStoreChanged(store);
     }
     this.initializedVolatile = true;
   }