[refactor](Nereids): cascades refactor (#9470)

Describe the overview of changes.

- rename GroupExpression
- use `HashSet<GroupExpression> groupExpressions` in `memo`
- add label of `Nereids` for CI
- remove `GroupExpr` from Plan

.github/workflows/labeler/scope-label-conf.yml

@@ -31,6 +31,9 @@ kind/test:
 area/vectorization:
   - be/src/vec/**/*
 
+area/nereids:
+  - fe/fe-core/src/main/java/org/apache/doris/nereids/**/*
+
 area/planner:
   - fe/fe-core/src/main/java/org/apache/doris/planner/**/*
   - fe/fe-core/src/main/java/org/apache/doris/analysis/**/*