Remove glyphDrawingMode

I think this property defaulting to `'paths'` is the reason for 50% of issues with emoji. Drawing glyphs is way, way faster. This is something we should do internally when needed: when text is filled with a gradient or stroked, we can use `cairo_glyph_path`, but normally, we should use `cairo_show_[text_]glyphs`.

Start by locating the glyphDrawingMode property and the text-rendering entry points that call Cairo. Confirm how gradient-filled or stroked text differs from ordinary text, then verify that the property is removed and the appropriate Cairo glyph behavior is used without regressing emoji rendering.

Written by the indexing model from the issue text.