Unity Tool: GameObject to Prefab

Add a Unity editor tool that can convert selected GameObjects into a prefab instance.

Expected behavior:
- The tool should be available from the Unity editor.
- It should preserve transform information when replacing objects with the chosen prefab.
- It should support applying a scale multiplier during conversion.

--- Original GitHub issue (auto-fetched) ---
Title: Unity Tool: GameObject to Prefab

Body:
**How will this enhancement improve the game?**
Mapping Team would like to have the option to convert GameObjects to Prefabs, while keeping transform information (position, rotation and scale)

**Describe the solution you'd like**
A new window in the Unity Editor in which a prefab can be loaded. Based on the selected objects in the scene hierarchy, and the press of a button, all of those will be replaced by

**Describe alternatives you've considered**
Alternative would be that mappers have to replace objects one by one, but tsk, we can automate stuff 😎
