Show a preview list of investments in the budget landing page

Note one of the tests dealing with random results is a bit flaky; since
it's a permutation selecting 7 objects out of 12, it will fail about
once every 4 million times. We think this is acceptable.

Co-Authored-By: Julian Nicolas Herrero <microweb10@gmail.com>

app/components/budgets/budget_component.html.erb

@@ -37,3 +37,5 @@
     </div>
   </div>
 </div>
+
+<%= render Budgets::InvestmentsListComponent.new(budget) %>