Clean up the dependencies for user image creation.

The dependency on MAKE_EXT4FS (mke2fs) has been covered by the rule for
MKEXTUSERIMG (mkuserimg_mke2fs):
https://android.googlesource.com/platform/system/extras/+/refs/heads/master/ext4_utils/Android.bp

The dependency on mksquashfs and img2simg comes from mksquashfsimage.sh,
which has been moved into mksquashfsimage's building rule.

This CL also fixes the ordering of INTERNAL_USERIMAGES_BINARY_PATHS,
which should come after adding all the binaries to
INTERNAL_USERIMAGES_DEPS.

Test: TreeHugger
Change-Id: I8b30bf87860d9711e88eecca4b76db72f5cd8241