fix potential GetStatistics hanging during rolling update; enable statistics by default (ydb-platform#9973)

Author: alexd65536

ydb/core/protos/feature_flags.proto

@@ -118,7 +118,7 @@ message TFeatureFlags {
     optional bool SuppressCompatibilityCheck = 103 [default = false];
     optional bool EnableUniqConstraint = 104 [default = true];
     optional bool EnableChangefeedDebeziumJsonFormat = 105 [default = false];
-    optional bool EnableStatistics = 106 [default = false];
+    optional bool EnableStatistics = 106 [default = true];
     optional bool EnableUuidAsPrimaryKey = 107 [default = true];
     optional bool EnableTablePgTypes = 108 [default = false];
     optional bool EnableLocalDBBtreeIndex = 109 [default = false];