Add templates left over from 8daef527.

Since I didn't create a true merge commit in a1eabb5a it didn't carry
over the earlier commit above.

Manually port the templates to this branch.

Stan wrote the templates, so he gets the credit :)

[Stan Lo & Kasper Timm Hansen]

actionview/test/fixtures/test/_cached_nested_cached_customer.erb

+<% cache cached_customer do %>
+  <%= render partial: "test/cached_customer", locals: { cached_customer: cached_customer } %>
+<% end %>

actionview/test/fixtures/test/_nested_cached_customer.erb

+<%= render partial: "test/cached_customer", locals: { cached_customer: cached_customer } %>