Get rid of Webpack rails-erb-loader

[dunkOnIT]

Mostly relates to data fetching from the Ruby backend. The replacement should be a (global?) store that holds data like events, formats, genders, currencies, etc. that are currently recignised by our code.

• Everything under webpacker/lib/wca-data
  • rails-env.js.erb feels very silly to export to JS, and we currently only need it for one single hack to avoid map geocoding calls during testing. Figure out a better way to handle this.
• webpacker/lib/requests/routes.erb (hardcode? load routing table from backend dynamically?)
• webpacker/lib/leaflet-wca/wca-provider.js.erb (why is this even an ERB in the first place?)