Calculate the amount of disk space the block & undo files currently use
Declared in <node/blockstorage.h>
[[requires_capability(0x7fbc8f17b428), requires_capability(0x7fbca3f04958), requires_capability(0x7fbcace16ba8), requires_capability(0x7fbca6c58818), requires_capability(0x7fbcad35ffb8), requires_capability(0x7fbc9fba1d78)]]
uint64_t
CalculateCurrentUsage();The total size in bytes of the block and undo files on disk.