Concat INTERNAL_*IMAGE_FILES into INTERNAL_ALLIMAGES_FILES

As we add more partitions, INTERNAL_*IMAGE_FILES variables has grown
and the places where the variables are referenced had to be touched
everytime. This change introduces a new variable
INTERNAL_ALLIMAGES_FILES which concatnates INTERNAL_*IMAGE_FILES, and
replaces the uses of the variables with the new one.

Bug: N/A
Test: m
Change-Id: I62a0f725a0f6999421d04a6261370be9124e62d7