[test/ffi] Re-enable disabled tests

Undo commenting out of tests in https://dart-review.googlesource.com/c/sdk/+/121422

Change-Id: I51acc1fd23f93007b4e75c1b641a325027136c58
Cq-Include-Trybots: luci.dart.try:vm-ffi-android-debug-arm-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/136220
Reviewed-by: Martin Kustermann <kustermann@google.com>
Commit-Queue: Daco Harkes <dacoharkes@google.com>

tests/ffi/function_structs_test.dart

@@ -21,8 +21,8 @@ typedef NativeCoordinateOp = Pointer<Coordinate> Function(Pointer<Coordinate>);
 
 void main() {
   testFunctionWithStruct();
-  // testFunctionWithStructArray();
-  // testFunctionWithVeryLargeStruct();
+  testFunctionWithStructArray();
+  testFunctionWithVeryLargeStruct();
 }
 
 DynamicLibrary ffiTestFunctions = dlopenPlatformSpecific("ffi_test_functions");