Add `cross_street` support to `/v1/structured`

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The /v1/structured API currently only supports address as input. This is not capable of parsing intersection queries which are supported by /v1/search and /v1/autocomplete. It would be nice to have feature-parity between the endpoints.

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A couple of potential solutions which come to mind:

• Implement parsing logic which generates two query clauses street & cross_street
• Add a new query parameter to the HTTP API called cross_street, the user then puts one street in the address parameter and the other street in the cross_street parameter.