[dynamic filtering] display dynamic filters for producers

In #623, we added a way to display dynamic filters for all consumers. Some producers, ex. SortExec display dynamic filters. We should support this.

Unlike consumers, this one is hard to implement because we only show one SortExec for the stage rather than 1 per task. Consumers were easier to do because we already display a different variant per task.

        ┌───── DistributedExec
        │ SortPreservingMergeExec: [MinTemp@0 DESC], fetch=10
        │   [Stage 1] => NetworkCoalesceExec: output_partitions=6, input_tasks=2
        └──────────────────────────────────────────────────
          ┌───── Stage 1 ── tasks=2, partitions=6
          │ SortExec: TopK(fetch=10), expr=[MinTemp@0 DESC], preserve_partitioning=[true], filter=[MinTemp@0 IS NULL OR MinTemp@0 > 17.2]
          │   DistributedLeafExec:
          │     t0: DataSourceExec: file_groups={3 groups: [[/testdata/weather/result-000000.parquet:<int>..<int>], [/testdata/weather/result-000000.parquet:<int>..<int>, /testdata/weather/result-000001.parquet:<int>..<int>], [/testdata/weather/result-000002.parquet:<int>..<int>]]}, projection=[MinTemp], file_type=parquet, predicate=DynamicFilter [ MinTemp@0 IS NULL OR MinTemp@0 > 17.2 ], dynamic_rg_pruning=eligible, pruning_predicate=MinTemp_null_count@0 > 0 OR MinTemp_null_count@0 != row_count@2 AND MinTemp_max@1 > 17.2, required_guarantees=[]
          │     t1: DataSourceExec: file_groups={3 groups: [[/testdata/weather/result-000000.parquet:<int>..<int>], [/testdata/weather/result-000001.parquet:<int>..<int>, /testdata/weather/result-000002.parquet:<int>..<int>], [/testdata/weather/result-000002.parquet:<int>..<int>]]}, projection=[MinTemp], file_type=parquet, predicate=DynamicFilter [ MinTemp@0 IS NULL OR MinTemp@0 > 17.2 ], dynamic_rg_pruning=eligible, pruning_predicate=MinTemp_null_count@0 > 0 OR MinTemp_null_count@0 != row_count@2 AND MinTemp_max@1 > 17.2, required_guarantees=[]
          └──────────────────────────────────────────────────

Start by reading the dynamic-filter display work from #623 and trace how consumer variants are rendered per task. Focus on the producer-side SortExec and the stage-level representation, including SortPreservingMergeExec and NetworkCoalesceExec. Done means producer dynamic filters appear correctly even when only one SortExec is shown for the stage.