Tweak flag classes for Library (#7829)

* Tweak flag classes for Library

- Add interface for Flag and Mask
- Merge Sort Type and Direction into one class
- Use custom serializers for preferences
  - Mainly to not break the old

* Review changes

app/src/main/sqldelight/data/categories.sq

@@ -16,6 +16,12 @@ BEGIN SELECT CASE
     END;
 END;
 
+getCategory:
+SELECT *
+FROM categories
+WHERE _id = :id
+LIMIT 1;
+
 getCategories:
 SELECT
 _id AS id,