EXPLAIN ANALYZE metrics should be sorted alphabetically

[progval]

Is your feature request related to a problem or challenge?

From ParquetExec metrics, with predicate pushdown enabled:

metrics=[output_rows=0, elapsed_compute=96ns, row_groups_matched_bloom_filter=0, row_groups_matched_statistics=21050, file_scan_errors=0, pushdown_rows_matched=0, row_groups_pruned_statistics=173576, row_groups_pruned_bloom_filter=21050, file_open_errors=0, num_predicate_creation_errors=0, bytes_scanned=25023432248, pushdown_rows_pruned=0, page_index_rows_pruned=0, predicate_evaluation_errors=0, page_index_rows_matched=0, time_elapsed_scanning_until_data=16.622753ms, time_elapsed_processing=72.280463608s, pushdown_eval_time=382ns, page_index_eval_time=3.177676ms, time_elapsed_scanning_total=16.661811ms, time_elapsed_opening=102.989073638s]

For example, pushdown_rows_matched and pushdown_rows_pruned are far away from each other, even though they refer to roughly the same thing.

The unstable sort also makes it hard to compare multiple EXPLAIN ANALYZE results.

Describe the solution you'd like

Sort them alphabetically, to break ties in the (very) partial order induced by MetricValue::display_sort_key

Describe alternatives you've considered

Split Metrics by categories and display each on a line; or split ParquetExec into "virtual" execution plans to reflect the successive opening and filtering steps done in ParquetOpener. That is more work, though.

Additional context

No response