We aren't using the size index. It has runtime and code maintenance
costs that aren't worth paying. Let's remove it.
Removing it from the format and no longer maintaining it are straight
forward.
The bulk of this patch is actually the act of removing it from the index
locking functions. We no longer have to predict the size that will be
stored during the transaction to lock the index items that will be
created during the transaction. A bunch of code to predict the size and
then pass it into locking and transactions goes away. Like other inode
fields we now update the size as it changes.
Signed-off-by: Zach Brown <zab@versity.com>