fix: release interning state before terminal output to fix hash aggregate regression (#23178)

[bhonepyisone]

What

Fixes the hash aggregate output performance regression introduced by #23055.

Problem

PR #23055 introduced EmitTo::First(batch_size) for incremental hash aggregate output. During the terminal output phase (Outputting state), no more intern() calls happen, but emit(EmitTo::First(n)) still maintained the hash lookup state on every output batch:

Implementation	Wasted work per batch
GroupValuesColumn (multi-col)	map.retain() with complex index-list manipulation
GroupValuesPrimitive (single-col)	map.retain() shifting all remaining indexes
GroupValuesRows (fallback)	Rebuilds rows + map.retain()

This caused O(groups × output_batches) unnecessary work.

Performance Impact

On TPC-DS SF10 query 23 with 24 target partitions:

• Before refactor(hash-aggr): Use EmitTo to output #23055: ~2.43s mean
• After refactor(hash-aggr): Use EmitTo to output #23055 (regressed): ~8.04s mean
• With this fix: should return to ~2.43s

The problematic node spent ~32s in emitting_time vs ~3s in actual aggregation time.

Fix

Added release_interning_state() to the GroupValues trait, called once during the Building → Outputting state transition in start_outputting(). It clears the hash map and interning buffers, making retain a no-op during terminal output.

The group values themselves are stored separately (in values / group_values / column builders) and are not cleared, so output data is preserved.

Files Changed

• group_values/mod.rs — Added release_interning_state() to the GroupValues trait
• aggregate_hash_table/common.rs — Call it in start_outputting()
• multi_group_by/mod.rs — Clear map, hashes, group-index lists (the main hot path)
• row.rs — Clear map, hashes, row buffers
• single_group_by/primitive.rs — Clear map
• single_group_by/boolean.rs — No-op (no hash map)
• single_group_by/bytes.rs — No-op (map rebuilt on emit)
• single_group_by/bytes_view.rs — No-op (map rebuilt on emit)

Closes #23178

[2010YOUY01]

Fixed in #23182