refactor: initialize additional fields in DataFile structure for aggregate tests

Author: Joe-Abraham

src/iceberg/test/aggregate_test.cc

@@ -442,11 +442,24 @@ TEST(AggregateTest, DataFileAggregatorParity) {
                                 .content_size_in_bytes = std::nullopt,
                                 .partition_spec_id = std::nullopt};
 
-  DataFile missing_some_stats{
-      .file_path = "file_missing_stats.avro",
-      .record_count = 20,
-      .value_counts = {{1, 20}, {4, 10}},
-  };
+  DataFile missing_some_stats{.file_path = "file_missing_stats.avro",
+                              .partition = {},
+                              .record_count = 20,
+                              .column_sizes = {},
+                              .value_counts = {{1, 20}, {4, 10}},
+                              .null_value_counts = {},
+                              .nan_value_counts = {},
+                              .lower_bounds = {},
+                              .upper_bounds = {},
+                              .key_metadata = {},
+                              .split_offsets = {},
+                              .equality_ids = {},
+                              .sort_order_id = std::nullopt,
+                              .first_row_id = std::nullopt,
+                              .referenced_data_file = std::nullopt,
+                              .content_offset = std::nullopt,
+                              .content_size_in_bytes = std::nullopt,
+                              .partition_spec_id = std::nullopt};
   auto [b4_lower, b4_upper] = make_bounds(1, -3, 1333);
   missing_some_stats.lower_bounds = std::move(b4_lower);
   missing_some_stats.upper_bounds = std::move(b4_upper);