"Skilled" villagers without job site do not get precedence over unemployed villagers

The bug

Villagers already skilled in profession (i.e. apprentice, journeyman, expert, master) but without job site do not get precedence over unemployed villagers when a that job site block becomes available.

Because "skilled" villagers do not lose their profession, this can lead to an unemployed villager being assigned that already has a "skilled unemployed" villager with that profession.

These villagers are unable to trade further once trade cap as they do not have a job site block.

Ideally, when a new job site block becomes available it should search for any "skilled" villager which does not have a job site block assigned before assigning to an unemployed villager.

How to reproduce

1. Create or find a "village" and have some unemployed villagers
2. Add a job site block (this should now be assigned to a villager)
3. Trade with the villager until they are "skilled"
4. Destroy job site block
5. Add same job site block in village
   → This will now be assigned to a villager, this could be an unemployed villager instead of a villager already skilled in that profession