fix(substrait): preserve grouping set output order

[bvolpato]

Which issue does this PR close?

• Closes Handling of Aggregates with multiple groupings sets is incorrect #17910.

Rationale for this change

For multiple grouping sets, Substrait orders aggregate output as grouping expressions, measures, then grouping-set ID. DataFusion puts its internal __grouping_id before measures. The consumer applied RelCommon.emit to DataFusion's order, so a mapping such as [0, 1, 2] returned __grouping_id where the plan requested its first measure.

See the Substrait AggregateRel output mapping specification.

What changes are included in this PR?

• Reorder consumer output to Substrait's direct order before applying emit mappings.
• Emit a producer mapping back to DataFusion's aggregate order.
• Deduplicate producer grouping expressions used by grouping references.
• Test both issue reproducer and two-measure roundtrip.

Are these changes tested?

• cargo test -p datafusion-substrait --features protoc
• cargo clippy --all-targets --all-features -- -D warnings

Are there any user-facing changes?

Substrait plans with multiple grouping sets now return emitted columns in specified order. No public API change.