Change package peergos.shared.cbor to io.ipld.cbor

@ianopolous would you accept & merge a PR which changed the package here from `peergos.shared.cbor` to `io.ipld.cbor`?

No files or tests are named. Locate every Java source and reference using peergos.shared.cbor, determine whether the package rename is intended across the repository, then update the package consistently and verify the existing build and tests pass.

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