feat: Switch from Namefilter to Name Accumulators

[matheus23]

Work on name accumulators (spec WIP: wnfs-wg/spec#65).

[appcypher]

This is a big and important change. Great work @matheus23! This should 🤞🏾 round up work on format stabilisation. The accumulator implementation looks good to me so I don't have much comment there. Just bits of nits here and there.

Now that we have *Forest::load/store helper functions, some lines like the one below need update:

rs-wnfs/wnfs/examples/private.rs

Line 68 in 122fa2a

let forest_cid = store.put_async_serializable(forest).await?;

Update to CryptoRngCore:

rs-wnfs/wnfs/src/lib.rs

Line 19 in 122fa2a

pub use rand_core::RngCore;

[matheus23]

@appcypher I decided to remove the hash algorithm generic type from the HamtForest. However, this means that we can no longer do tests with a MockHasher.
But I decided to go ahead and remove that test. It's quite a long test (hard to maintain), and I'd expect most of the code it covers would also be covered by the proptests in wnfs-hamt.

[appcypher]

LGTM! 🎉