BUG: use EA.astype in ExtensionBlock.to_native_types
Closes https://github.com/pandas-dev/pandas/issues/28840

This implements a `ExtensionBlock.to_native_types` to override the base class which converts to a numpy array.

To test this is a bit tricky. The current JSONArray we have in the extension tests does not have this issue. I would need to implement and add tests for a new ListArray to check this (I can ensure that this fixes the geopandas issue)