switches to 6141039ad8
changes since 5cf22196ad0b:
- refactor(unixfs): use arithmetic for exact block size calculation
- refactor(unixfs): unify size tracking and make SizeEstimationMode immutable
- feat(unixfs): optimize SizeEstimationBlock and add mode/mtime tests
also clarifies that directory sharding globals affect both `ipfs add` and MFS.