runtime: move value formatting functionality to a dedicated api

bshell.runtime/runtime/eval.c

@@ -353,10 +353,8 @@ static enum bshell_status eval_instruction(
 		}
 
 		int end_of_data = 0;
-		bool columns_initialised = false;
 		fx_value record = FX_VALUE_EMPTY;
-		struct bshell_table_ctx table_ctx;
-		bshell_table_ctx_init(&table_ctx, fx_stdout);
+		bshell_runtime_begin_output(rt);
 		while (1) {
 			bstatus = bshell_pipeline_pump_record(
 				pipeline,
@@ -371,22 +369,11 @@ static enum bshell_status eval_instruction(
 				continue;
 			}
 
-			if (!columns_initialised) {
-				const fx_type *ty
-					= fx_type_get_by_id(record.v_type);
-				bshell_table_ctx_prepare_columns_from_format(
-					&table_ctx,
-					ty,
-					NULL);
-				bshell_table_ctx_print_headers(&table_ctx);
-				columns_initialised = true;
-			}
-
-			bshell_table_ctx_print_record(&table_ctx, &record);
+			bshell_runtime_output_value(rt, &record);
 			fx_value_unset(&record);
 		}
 
-		bshell_table_ctx_cleanup(&table_ctx);
+		bshell_runtime_end_output(rt);
 		bshell_pipeline_unref(pipeline);
 		break;
 	}