Describe the bug

The logic within MapArrayReader will not work if the MapArray is itself nested, in particular:

• It does not expose the def_level / rep_levels of its children
• It assumes that a repetition level of 0 corresponds to a new map entry

To Reproduce

A nullable StructArray with a child MapArray will likely result in an error, similarly a ListArray with a child MapArray will likely error

Expected behavior

This should be properly supported