[Impeller] Need a public Skia API to look up whether a font+glyph is a bitmap or COLR font

Current approach is:

```
SkStrikeSpec strikeSpec = SkStrikeSpec::MakeWithNoDevice(run.font());
SkBulkGlyphMetricsAndPaths paths{strikeSpec};
auto is_color = paths.glyph(glyphs[i])->isColor();
```

Which requires private includes. While we can construct our own Glyph instance using the glyph_ids we get from SkParagraph, these don't have any of the color/bitmap fields populated.