[regression](fuzzy)fuzzy enable_fold_constant_by_be (#16448)

* [fuzzy](test) fuzzy some session variables stably according to pull_request_id

* fuzzy enable_fold_constant_by_be

---------

Co-authored-by: stephen <hello_stephen@@qq.com>

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

@@ -1979,5 +1979,11 @@ public class Config extends ConfigBase {
 
     @ConfField(mutable = false)
     public static int topn_two_phase_limit_threshold = 512;
+
+    /**
+     * Used to set session variables randomly to check more issues in github workflow
+     */
+    @ConfField(mutable = true)
+    public static int pull_request_id = 0;
 }