Stats should be logged in INFO level (#4977)

Summary:
Previously, stats were logged in warning level. This was done in that way because
people reported that it wasn't logged in MyRocks. However, later we learned that it turns
out to be due to a bug in MyRocks, which is fixed in
79bb705e74

Now we revert the stats logging to INFO level, so that it doesn't pollute the warning
level logging.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4977

Differential Revision: D14058485

Pulled By: siying

fbshipit-source-id: 19fab323c19d9bc88184287f209551f9a77ca0e6

db/db_impl.cc

@@ -613,7 +613,7 @@ const Status DBImpl::CreateArchivalDirectory() {
 void DBImpl::PrintStatistics() {
   auto dbstats = immutable_db_options_.statistics.get();
   if (dbstats) {
-    ROCKS_LOG_WARN(immutable_db_options_.info_log, "STATISTICS:\n %s",
+    ROCKS_LOG_INFO(immutable_db_options_.info_log, "STATISTICS:\n %s",
                    dbstats->ToString().c_str());
   }
 }
@@ -665,16 +665,16 @@ void DBImpl::DumpStats() {
     }
   }
   TEST_SYNC_POINT("DBImpl::DumpStats:2");
-  ROCKS_LOG_WARN(immutable_db_options_.info_log,
+  ROCKS_LOG_INFO(immutable_db_options_.info_log,
                  "------- DUMPING STATS -------");
-  ROCKS_LOG_WARN(immutable_db_options_.info_log, "%s", stats.c_str());
+  ROCKS_LOG_INFO(immutable_db_options_.info_log, "%s", stats.c_str());
   if (immutable_db_options_.dump_malloc_stats) {
     stats.clear();
     DumpMallocStats(&stats);
     if (!stats.empty()) {
-      ROCKS_LOG_WARN(immutable_db_options_.info_log,
+      ROCKS_LOG_INFO(immutable_db_options_.info_log,
                      "------- Malloc STATS -------");
-      ROCKS_LOG_WARN(immutable_db_options_.info_log, "%s", stats.c_str());
+      ROCKS_LOG_INFO(immutable_db_options_.info_log, "%s", stats.c_str());
     }
   }
 #endif  // !ROCKSDB_LITE