⚡ Add performance improvements to file thumbnails

Mainly addresing unnecesary object transmission. The new code strips
unnecesary data to be transferred from back to front.

Additionally it removes some legacy code and simplifies other
parts of code.

common/src/app/common/spec/shape.cljc

@@ -53,6 +53,7 @@
 
 (s/def ::hide-fill-on-export boolean?)
 
+(s/def ::file-thumbnail boolean?)
 (s/def ::masked-group? boolean?)
 (s/def ::font-family string?)
 (s/def ::font-size ::us/safe-integer)
@@ -301,7 +302,8 @@
 
 (defmethod shape-spec :frame [_]
   (s/and ::shape-attrs
-         (s/keys :opt-un [::hide-fill-on-export])))
+         (s/keys :opt-un [::file-thumbnail
+                          ::hide-fill-on-export])))
 
 (s/def ::shape
   (s/and (s/multi-spec shape-spec :type)