Use API to geocode searches rather than react-geocode

[RyanTG]

On the website, we recently improved geocoding results by including nominatim as a fallback. However, this isn't possible with the react-geocode.

Instead of using that package, let's use our API for geocoding searches.

It seems like we would have to continue using react-geocode for Events.

[RyanTG]

Alternative: use expo-location for geocoding.

I think for Search.js it would be a geocode (converting address into lat/lon) and for Events.js it would be reversegeocode (converting lat/lon into formattedAddress... although I now see that formattedAddress is Android-only, so maybe this wouldn't work for us).