allow walk access or egress for ride_hail_transit

[zneedell]

Previously we only allowed itineraries of rh -> transit -> rh when the mode ride_hail_transit was selected. This should allow for either the access or egress leg to be walk. There's nothing explicitly preventing the router from constructing a walk_transit itinerary as well, but that one should be filtered out in ChoosesMode if it is not allowed based on the agent's input plans.

This PR also captures RH cost in router so that we don't have as many routes with really long ride-hail legs and short transit legs

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This change is