Support FeatureCollection and MultiPolygon in geozones

We're reworking the format validation to correctly interpret feature
collection, feature, and geometry, according to RFC 7946 [1].

Since Leaflet interprets GeoJSON format, we're rendering the GeoJSON as
a layer instead of as a set of points. For that, we're normalizing the
GeoJSON to make sure it contains either a Feature or a
FeatureCollection. We're also adding the Leaflet images to the assets
path so the markers used for point geometries are rendered correctly.

Note we no longer allow a GeoJSON containing a geometry but not a
defined type. Since there might be invalid GeoJSON in existing Consul
Democracy databases, we're normalizing these existing geometry objects
to be part of a feature object.

We're also wrapping the outline points in a FeatureCollection object
because most of the large GIS systems eg ArcGIS, QGIS export geojson as
a complete FeatureCollection.

[1] https://datatracker.ietf.org/doc/html/rfc7946

Co-authored-by: Javi Martín <javim@elretirao.net>

config/application.rb

@@ -125,6 +125,7 @@ module Consul
     config.assets.paths << Rails.root.join("app", "assets", "fonts")
     config.assets.paths << Rails.root.join("vendor", "assets", "fonts")
     config.assets.paths << Rails.root.join("node_modules", "jquery-ui", "themes", "base")
+    config.assets.paths << Rails.root.join("node_modules", "leaflet", "dist")
     config.assets.paths << Rails.root.join("node_modules")
 
     config.active_job.queue_adapter = :delayed_job