[api-minor] Use a local font or fallback on an embedded one (if it exists) for non-embedded fonts (bug 1766039)

- Replace FoxitSans with LiberationSans: LiberationSans is already there (for XFA) and we can use
it as a good replacement of FoxitSans.
- For now we just try to substitue standard fonts, the strategy is the following:
  * we try to find a font locally from a hardcoded list;
  * if it fails then we use Liberation as fallback (only for Helvetica for the moment);
  * else we just fallback on the system serif/sansserif/monospace font.

src/core/fonts.js

@@ -98,6 +98,7 @@ const EXPORT_DATA_PROPERTIES = [
   "name",
   "remeasure",
   "subtype",
+  "systemFontInfo",
   "type",
   "vertical",
 ];
@@ -998,6 +999,7 @@ class Font {
       this.fallbackName = "sans-serif";
     }
 
+    this.systemFontInfo = properties.systemFontInfo;
     this.differences = properties.differences;
     this.widths = properties.widths;
     this.defaultWidth = properties.defaultWidth;