Adding SectorCheckedBlock to VolumeManager's possible IO operations. This writes a block at a time of sector checked data.
Using SectorCheckedBlock to zero-out append log on new file-service creation. This dramatically reduces (fresh) startup io cost.
Adding flag to file service (defaults to true) to control whether it throws or aborts on corrupt append-logs. This is useful for testing the logic (it's hard to catch an abort in a unit test)
Use SectorCheckedBlock to read in the append-log block by block as opposed to sector by sector. This greatly reduces the start-up io cost when reconstructing from an existing disk image. Since we abort on any append log corruption, there's no need to read the sectors in one by one.