Run all AsyncTasks on thread pool executor

Should Fix #7002

src/org/thoughtcrime/securesms/components/emoji/RecentEmojiPageModel.java

@@ -89,7 +89,7 @@ public class RecentEmojiPageModel implements EmojiPageModel {
 
         return null;
       }
-    }.execute();
+    }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
   }
 
   private String[] toReversePrimitiveArray(@NonNull LinkedHashSet<String> emojiSet) {

src/org/thoughtcrime/securesms/components/emoji/parsing/EmojiPageBitmap.java

@@ -62,7 +62,7 @@ public class EmojiPageBitmap {
         @Override protected void onPostExecute(Void aVoid) {
           task = null;
         }
-      }.execute();
+      }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
     }
     return task;
   }