Although known for a while, this was triggered by documentation work related to #14695.

• Integration tests for embedded render hooks are in tpl/tplimpl/render_hook_integration_test.go.
• Integration test for embedded shortcodes are in tpl/tplimpl/shortcodes_integration_test.go.

However, integration tests for the remaining embedded templates (Disqus, Google Analytics, Open Graph, Pagination, Schema, and X/Twitter Cards) are not consolidated, and there are substantial coverage holes regarding tpl/tplimpl/embedded/templates/_partials/_funcs/get-page-images.html.