Move iterator support functions out of ChapelArray and into a new module

Added a new internal module for iterator support functions and moved the
functions out of ChapelArray.  Updated tests that expected errors/warnings
from these functions to come from ChapelArray.  Updated a test that counts
dead modules to expect one more.
I notice this is much earlier than ChapelArray is used in the module list, what's the reasoning behind that?  (Not objecting, just curious)