Withdrawals to handle filling empty blocks when syncing

[jframe]

The empty block check is missing checking the withdrawals in the CompleteBlocksTask hasEmptyBody method. Not sure if this is necessary, we need to understand more about what this class is doing but we need to consider withdrawals here as well.

[jframe]

CompleteBlocksTask is used only for full sync and fast which are only used before the merge. Withdrawals must be enabled after the merge and after the merge, we use backward sync which doesn't use this task. So this isn't necessary for Withdrawals as will never be used when Withdrawals is active.