Check wantlists by multihash

[Winterhuman]

As mentioned at https://github.com/ipfs/kubo/issues/4189#issuecomment-1201802260, Bitswap apparently still checks wantlists by CID instead of multihash

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[guseggert]

Sounds reasonable. When we pick this up, make sure specs are up-to-date https://github.com/ipfs/specs/blob/main/BITSWAP.md#bitswap-110