While the `local.Local` backend is the only implementation of
`backend.Local`, creating the backend with `ForceLocal` bypasses the
`backend.Backend` in the `local.Local` causing a local state to be
implicitly created rather than using the configured state backend.
Add a test that imports into a configured backend (using the "local"
backend as a remote state proxy). This further confirms the confusing
nature of ForceLocal, as the backend _is_ local, but not from the
viewpoint of meta.Backend.
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