Implement to_bytes() on the arraySteams

Instead of each arraystream child implementing its own _render_element, we can make sure that each object in the array implements to_bytes() and call that in the for loop.

Start by locating the arraystream child classes and their _render_element implementations. Inspect how objects in each array are serialized, then determine whether they already expose to_bytes(). Done means the arraystream loop consistently calls to_bytes() instead of relying on child-specific _render_element methods.

Written by the indexing model from the issue text.