feat(Live.TripPlanner): wheelchair checkbox toggles groupings

[thecristen]

Asana Ticket: Trip Planner: group results based on newly fixed accessibility score (last task in TP | Update trip accessibility display)

Mainly UI changes here:

• "Prefer accessible trips" is unchecked - show itinerary summaries grouped by "Accessible Routes" follow by "Inaccessible Routes"
• "Prefer accessible trips" is checked - show itinerary summaries in a flat list (like now), limited only to those which are accessible (this was already done in feat(TripPlanner): filter itineraries if wheelchair: true set #2501)

Backend change:

• When requesting plans from OTP, always pass wheelchair: true to that, regardless of what's chosen in the form. This ensures that itineraries have a computed accessibility_score (and doesn't significantly impact which itineraries are returned thanks to the recent changes in feat: allow trips and stops of unknown wheelchair-accessibility otp-deploy#44)

Tip

Revised PR

Fixes some flawed assumptions, now has the following changes:

• "Prefer accessible trips" is unchecked - show itinerary summaries in a flat list (like now)
• "Prefer accessible trips" is checked - show itinerary summaries grouped by "Accessible Routes" followed by "Inaccessible Routes"
  No changes to how we make requests to OTP.