This change moves the vello encoding logic to a new crate under
crates/encoding. Combined with the `vello_shaders` crate, this enables
lightweight integration of the Vello pipelines into renderers that don't
depend on wgpu (or perhaps written in languages other than Rust).
The Scene/Fragment API currently remain the vello crate.
* reorganize GlyphCache::get_or_insert() to use the HashMap entry API
* change DrawGlyphs::hint() parameter name from `yes` to `hint` for clarity
* change Layout::path_data() to return bytes instead of [f32; 2]. Path segments could be encoded as i16, making this incorrect
* make SimpleText::add_run accept glyph_transform and style parameters so it doesn't unconditionally do oblique strokes
* replace fill/stroke methods on DrawGlyphs with a single draw method that accepts either fill or stroke styles
* update peniko rev to access the new style types used above
* for now, change glyph cache to only cache non-zero fills. Prior to this, style was ignored in the key which could lead to incorrect rendering.
