Change where localCopyPropagation happens in lowerIterators

We were running into a bug where localCopyPropagation would try and
access a field on an iterator class before it had been created. This is
caused by the fact that fixNumericalGetMemberPrims leaves the AST in an
invalid state that is later fixed in
replaceIteratorFormalsWithIteratorFields.

The fix was to move the calls to localCopyPropagation before
inlineIterators. In the future we may want to look at creating the
iterator class earlier and not inserting PRIM_GET_MEMBER calls with the
expected field index.

The call to fragmentLocalBlocks was removed as it was unnecessary after
this reshuffling.