Allow copy_efs_files_to_data to read efs block devices

Previously, we rely on mount points to copy files out of
efs partitions. Switch over to dump.f2fs to read directly
from block device without mounting. This allows us to copy
files out of efs partition in both 4K and 16K mode.

Test: Boot ext4 device with dev option enabled
Bug: 340965747
Change-Id: Ie3108319cfdb5d922a18863de7431c3cfcc4cf16