Move getRemoteCollectionItems to RemoteViewsFactory

This brings more accuracy when estimating the collection size as Bitmap
in the local service could share the same address, so the BitmapCache
could contain fewer duplicates. Additionally the ApplicationInfo will be
having the same address which allows us to utilize allowSquashing to
eliminate duplicate writes to the parcel

Manually verified that the size of the collection shrinks by ~33% from
600k to 400k

Test: Manual
Bug: 245950570
Change-Id: I16ddba00465e64613f6dbe836da6bd0693da7d4c