utilities: offer a way to enter a no-writeback critical section in a Cache, used in FatFile
ata: make AtaDisk::write synchronous again as it isn't being called from timer handlers anymore, and an asynchronous write can sometimes attempt to write an evicted cache page.

If asynchronous writing is required, we can look into pinning the cache
page or other similar solutions. However, synchronous AtaDisk::write should
not affect anything in the layer above that is using its own cache
correctly.