Get rid of CSS transform on each annotation in the annotation layer

- each annotation has its coordinates/dimensions expressed in percentage,
  hence it's correctly positioned whatever the scale factor is;
- the font sizes are expressed in percentage too and the main font size
  is scaled thanks a css var (--scale-factor);
- the rotation is now applied on the div annotationLayer;
- this patch improve the rendering of some strings where the glyph spacing
  was not correct (it's a Firefox bug);
- it helps to simplify the code and it should slightly improve the update of
  page (on zoom or rotation).

src/core/xfa/xhtml.js

@@ -182,6 +182,10 @@ function mapStyle(styleStr, node, richText) {
     );
   }
 
+  if (richText && style.fontSize) {
+    style.fontSize = `calc(${style.fontSize} * var(--scale-factor))`;
+  }
+
   fixTextIndent(style);
   return style;
 }