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When multiple grouped queries are combined via UNION ALL on randomly
distributed tables without PhysicalDistribute operators, Doris was
generating redundant local aggregation and global aggregation layers
without a distribute operator between them.

The issue was in the `banAggUnionAll` method in
ChildrenPropertiesRegulator, which was too aggressively forbidding
one-phase aggregation for all agg-union patterns, regardless of whether
the union inputs had PhysicalDistribute operators.

Modified the `banAggUnionAll` method to only forbid one-phase
aggregation when the union inputs actually have PhysicalDistribute
operators:

1. Checks each group in the union
2. Examines all physical expressions in each group
3. Only forbids one-phase agg if any input has PhysicalDistribute
4. Allows one-phase agg if no inputs have PhysicalDistribute

Added regression test `agg_union_group_by.groovy` to verify correct
behavior

Improved query optimization: Eliminated redundant aggregation layers in
UNION ALL queries with GROUP BY on randomly distributed tables.