[enhancement](Nereids) support StatementContext, SET_VAR, and Plan pre/post processor

[924060929]

Proposed changes

1. add StatementContext, and PlannerContext is renamed to CascadsContext. CascadsContext belong to a StatementContext, and StatementContext belong to a ConnectionContext, and the lifecycle increases in turn. StatementContext can wrap some statement's lifecycle-related state, such as ExpressionId, TableLock. MemoTestUtil can simplify create a CascadesContext and Memo for test.
2. add PlanPreprocessor to process parsed logical plan before copy into memo. and add a PlanPostprocessor to process physical plan after copy out from memo.
3. utilize PlanPreprocessor to process SET_VAR hint, the class is EliminateLogicalSelectHint
4. pass the limit clause in regression test case, in set_var.groovy

Checklist(Required)

1. Does it affect the original behavior:
   • [ ] Yes
   • [x] No
   • [ ] I don't know
2. Has unit tests been added:
   • [x] Yes
   • [ ] No
   • [ ] No Need
3. Has document been added or modified:
   • [ ] Yes
   • [ ] No
   • [x] No Need
4. Does it need to update dependencies:
   • [ ] Yes
   • [x] No
5. Are there any changes that cannot be rolled back:
   • [ ] Yes (If Yes, please explain WHY)
   • [x] No