Move executions image partial to a component

This way it'll be easier to write tests for it. We also get rid of
another helper file :).

app/components/budgets/executions/image_component.html.erb

@@ -1,5 +1,3 @@
-<% milestone = first_milestone_with_image(investment) %>
-
 <% if milestone&.image.present? %>
   <%= image_tag milestone.image.variant(:large), alt: milestone.image.title %>
 <% elsif investment.image.present? %>

app/components/budgets/executions/image_component.rb

@@ -0,0 +1,14 @@
+class Budgets::Executions::ImageComponent < ApplicationComponent
+  attr_reader :investment
+
+  def initialize(investment)
+    @investment = investment
+  end
+
+  private
+
+    def milestone
+      investment.milestones.order_by_publication_date
+                           .select { |milestone| milestone.image.present? }.last
+    end
+end

app/helpers/budget_executions_helper.rb

@@ -1,6 +0,0 @@
-module BudgetExecutionsHelper
-  def first_milestone_with_image(investment)
-    investment.milestones.order_by_publication_date
-                         .select { |milestone| milestone.image.present? }.last
-  end
-end

app/views/budgets/executions/_investments.html.erb

@@ -7,7 +7,7 @@
         <div class="small-12 medium-6 large-4 column end margin-bottom">
           <div class="budget-execution">
             <%= link_to budget_investment_path(@budget, investment, anchor: "tab-milestones"), data: { "equalizer-watch": true } do %>
-              <%= render "image", investment: investment %>
+              <%= render Budgets::Executions::ImageComponent.new(investment) %>
               <div class="budget-execution-info">
                 <div class="budget-execution-content">
                   <h5><%= investment.title %></h5>