Unexpected cbor code `0xa1` when decoding `banyan::index::Index<trees::axtrees::AxTrees>`.

This error basically says “I don’t want to read this dictionary of length 1”, which is the “kinded” representation of `Index` (DagCbor doesn’t like definite-length encoding, IIRC). I encountered this while developing event dump/restore functionality in Actyx. The restore part feeds events to `BanyanStore::append0` (to preserve timestamps) and does not mess with the internals, so I don’t see how my code could influence the encoding of a Banyan index block.

How much work would it be to replace all DagCbor with cbor-data? I trust that implementation much more, it is very thoroughly tested to actually accept all valid CBOR.

/cc @rklaehn