FIX: Show the last rendered user-tip (#29346)

…or a tip with the highest priority.

This regressed in 597ef1119536693ef0bc7fe799ff485047f9f6f7 where we got rid of `next()` calls, so we'd render the first tip we encounter.

The commit also adds a test and updates existing ones.

spec/system/user_tips_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-describe "Homepage", type: :system do
+describe "User tips", type: :system do
   fab!(:admin)
   fab!(:user)
   fab!(:topics) { Fabricate.times(2, :post).map(&:topic) }