Speed up squisher

-Parallelize opticharging
-Pre-apply the beats size reduction, rather than doing it EVERY TIME
-Rather than CP to repack.d, then MV back to ota, just symlink the temp location to where the originals are
-2048 > 1024

Change-Id: I110afe22cbdc3fe98f605f6ebeb7c7a646b78028