go-ipfs-blockstore v1.0.0

This release of go-ipfs-blockstore uses raw multihashes as keys when writing
to the underlying datastore rather than CIDs, as previously
happened.

Similarly, when querying a block by CID, it will use the raw multihash
embedded in that CID to perform the query, so it expects that blocks have been
stored using that raw multihash key.

THIS IS A BREAKING CHANGE, even if interfaces remain the same.This means that
applications based on previous go-ipfs-blockstore will need to migrate their
underlying storage and replace all CIDv1 keys with raw multihashes. CIDv0 keys
are not affected as they are a raw multihash already.
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