[refactor](nereids)make enable_stats session var (#25550)

this pr is used to test plan shape without column stats

fe/fe-common/src/main/java/org/apache/doris/common/Config.java

@@ -2016,12 +2016,6 @@ public class Config extends ConfigBase {
     @ConfField(mutable = true)
     public static boolean enable_round_robin_create_tablet = false;
 
-    /**
-     * If set false, user couldn't submit analyze SQL and FE won't allocate any related resources.
-     */
-    @ConfField
-    public static boolean enable_stats = true;
-
     /**
      * To prevent different types (V1, V2, V3) of behavioral inconsistencies,
      * we may delete the DecimalV2 and DateV1 types in the future.