is_retrofit_device to work in bootloader

Changing is_retrofit_device() to work in bootloader. Previously flashall
flow was to boot into fastbootd and then  make a call to get
"super-image-name", however this does not work in bootloader. Since all
tasks are generated ahead of time, this old check will now fail and we
will fail to add the correct delete tasks in collectTasks(). This change
does make it so that is_retrofit check only works during fastboot
flashall + fastboot update (since this function is only used here,
nothing is currently affected).

To determine if a device is retrofit, it must satisfy two conditions -> Has
dynamic partitions && does not contain a super partition. The check for
if source has super_empty.img is sufficient for determining if a device
has dynamic partitions and if any single partition has
LP_PARTITION_ATTR_SLOT_SUFFIXED it is determined to be retrofit

Test: logs from fastboot update on sargo device confirms this check
returns true. Fastboot update on sargo
Bug: 300287332

Change-Id: Iadf5c56de51993a79307c60e45d6cc4988436f23