feat(combobox): use ComboboxComponent on drop_down_list champs

app/components/editable_champ/drop_down_list_component/drop_down_list_component.html.haml

@@ -18,6 +18,8 @@
           = @form.radio_button :value, Champs::DropDownListChamp::OTHER, checked: @champ.other?, id: "#{@champ.id}_radio_option_other"
           %label.fr-label{ for: "#{@champ.id}_radio_option_other" }
             Autre
+  - elsif @champ.render_as_combobox?
+    = render Dsfr::ComboboxComponent.new form: @form, name: :value, options: @champ.enabled_non_empty_options, selected: @champ.selected, id: @champ.input_id, class: select_class_names, describedby: @champ.describedby_id
   - else
     = @form.select :value,
       @champ.options.compact_blank,

app/models/champs/drop_down_list_champ.rb

@@ -1,6 +1,7 @@
 class Champs::DropDownListChamp < Champ
   store_accessor :value_json, :other
   THRESHOLD_NB_OPTIONS_AS_RADIO = 5
+  THRESHOLD_NB_OPTIONS_AS_AUTOCOMPLETE = 20
   OTHER = '__other__'
   delegate :options_without_empty_value_when_mandatory, to: :type_de_champ
 
@@ -10,6 +11,10 @@ class Champs::DropDownListChamp < Champ
     enabled_non_empty_options.size <= THRESHOLD_NB_OPTIONS_AS_RADIO
   end
 
+  def render_as_combobox?
+    enabled_non_empty_options.size >= THRESHOLD_NB_OPTIONS_AS_AUTOCOMPLETE
+  end
+
   def options?
     drop_down_list_options?
   end