Codechange: Make SpriteType, CargoSortType, SourceType and ScriptType enum classes. (#10663)

This avoids a (soft) namespace conflict between the four ST_* enums.

src/fontcache/freetypefontcache.cpp

@@ -241,7 +241,7 @@ const Sprite *FreeTypeFontCache::InternalGetGlyph(GlyphID key, bool aa)
 	/* FreeType has rendered the glyph, now we allocate a sprite and copy the image into it */
 	SpriteLoader::Sprite sprite;
 	sprite.AllocateData(ZOOM_LVL_NORMAL, static_cast<size_t>(width) * height);
-	sprite.type = ST_FONT;
+	sprite.type = SpriteType::Font;
 	sprite.colours = (aa ? SCC_PAL | SCC_ALPHA : SCC_PAL);
 	sprite.width = width;
 	sprite.height = height;