[regression_test](debug) add regression test case for session variable skip_storage_engine_merge, skip_delete_predicate and show_hidden_columns

[jacktengg]

Proposed changes

Issue Number: close #xxx

Problem summary

Related to #11952 , add regression test case for session variable skip_storage_engine_merge, skip_delete_predicate and show_hidden_columns.

Also add this function to new olap scan node.

Checklist(Required)

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

Further comments

If this is a relatively large or complex change, kick off the discussion at dev@doris.apache.org by explaining why you chose the solution you did and what alternatives you considered, etc...

[yiguolei]

LGTM