[test] Add generated tests for emoji clusters Fixes https://github.com/harfbuzz/harfbuzz/issues/3017 Uses AdobeBlank2.ttf from: https://github.com/adobe-fonts/adobe-blank-2 instead of a dummy empty font so that everything maps to GID 1 and control code points are kept instead of being dropped because there is not space glyph (otherwise we’d need to identify control code points somehow when generating the expectations).