font/coretext: discovery scoring should take into account symb. traits

Fixes #707

Our scoring algorithm previously did not take into account symbolic
traits, so when `bold = false and italic = false`, regular, bold, italic
would all be equally likely to appear first.

This modifies our scoring algorithm to prioritize matching symbolic
traits. Further, we have a special case for no symbolic traits to
prioritize "Regular" named styles. We can expand this to other styles
too but we do not do this here.

We also modified the algorithm to always prefer fonts with more glyphs
over fonts with less, hopeful that we can load fewer fonts for other
glyphs later.

pkg/macos/text/font.zig

@@ -47,6 +47,10 @@ pub const Font = opaque {
         return @ptrCast(@constCast(c.CTFontCopyFontDescriptor(@ptrCast(self))));
     }
 
+    pub fn getGlyphCount(self: *Font) usize {
+        return @intCast(c.CTFontGetGlyphCount(@ptrCast(self)));
+    }
+
     pub fn getGlyphsForCharacters(self: *Font, chars: []const u16, glyphs: []graphics.Glyph) bool {
         assert(chars.len == glyphs.len);
         return c.CTFontGetGlyphsForCharacters(