Part of #19795

As with_new_children clones the most fields of the plan, we could make clone cheaper, arcing immutable parts that may be long (projection, different expressions), the issue suggests to:

• Store projection as Option<Arc<[usize]>> instead of Option<Vec<usize>> in FilterExec, HashJoinExec, NestedLoopJoinExec.
• Store exprs as Arc<[ProjectionExpr]> instead of Vec in ProjectionExprs.
• Store arced aggregation and filter expressions within AggregateExec.
• Store arced expr, null_expr, groups in PhysicalGroupBy.

Also, to simplify implementation, we could improve project_schema and Statistics::project methods to get Option<impl AsRef<[usize]>> instead of the Option<&Vec<usize>> as Option<&Vec> always could be borrowed as deref.