Restore get_media_embedded_in_content() and test_post_gallery_images() and use their new function names. see #24202

git-svn-id: https://unit-tests.svn.wordpress.org/trunk@1313 4a5a2adb-35eb-4268-9a1b-fe04a4134342
Remove test_the_content_with_id(). ID supports was removed in [24598]. see #24330

git-svn-id: https://unit-tests.svn.wordpress.org/trunk@1314 4a5a2adb-35eb-4268-9a1b-fe04a4134342