We can't check lineage in the remote state instance, because we may need
to overwrite a state with a new lineage. Whil it's tempting to add an
optional interface for this, like OverwriteState(), optional interfaces
are never _really_ optional, and will have to be implemented by any
wrapper types as well.
Another solution may be to add a State.Supersedes field to indicate that
we intend to replace an existing state, but that may not be worth the
extra check either.
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