LogicalPlan::map_children should recurse into table scans defined by a plan #19272
Description
Describe the bug
This is about the TreeNode impl for LogicalPlan. Some LogicalPlan::TableScan are not actually leaves because they are defined by a logical plan. However here:
datafusion/datafusion/expr/src/logical_plan/tree_node.rs
Lines 348 to 349 in 321401c
The fn map_children is unconditionally assuming that the table scan is a leaf and has no children.
The correct behaviour would be to recurse into the plan, if one exists.