Mapper typing: Array->Array, Names->Names (#610)

* Mapper typing: Array->Array, Names->Names

* more typing work

* More type fixes

* MappedT -> ArrayOrNamesT

* handle DictOfNamedArrays in materialize_with_mpms outside of the mapper

* a few more tweaks

* add deduplicate

* fix doc

* Update baseline

---------

Co-authored-by: Matthew Smith <mjsmith6@illinois.edu>