Copy features array before passing them to core

[LukasPaczos]

Closes #14565.

I have noticed, that the only possible scenario when the crash from #14565 can occur is when the collection is cleared while it's being converted to an array on our worker thread:

mapbox-gl-native/platform/android/src/geojson/feature_collection.cpp

Line 14 in 316584f

auto jFeatures = java::util::List::toArray<Feature>(env, jFeatureList);

ArrayList#toArray builds an array with a fixed size, adding a null padding if necessary, therefore I think, that the collection has to be cleared on one thread, right when the ArrayList#toArray is copying the list on the other (after setting the resulting array's size and before finishing copying all of the elements, which creates the null padding).

This is a race condition, so the only test I was able to come up with is a brute force. The test has been reliably reproducing the crash for me on every single run, either on a physical device or an emulator.

The solution is to copy the features array to a new array so that it cannot be modified by the provider. I was considering copying each Feature object as well, but it's not critical as modifying the feature should be safe and it introduced additional overhead.

[LukasPaczos]

Ready for another round.