alreadyLightmapped API needs better support to work with new light modes.

Reproduction steps:
1) Download the new reproducible project `alreadyLightmapped.zip` from comments section below
2) Open the scene `TestScene`
3) Disable Obj2 so it's not visible
4) Generate lighting
5) In play mode, click on `alreadyLightmapped` button on top of the screen
6) Observe the inconsistent lighting across baked and dynamic objects, lighting is overexposed
7) Click on `alreadyLightmapped` button again
8) Observe that only lightmap static objects are correctly lit.

Notes:
- Regression introduced in: 5.6.0b2 with new light modes
- A gif that shows the process is shared below
- In the scene, there is one mixed directional light and light mode is set to subtractive
- Non-Baked objects are disabled before baking the scene and have no lightmap data. These should be lit realtime by the light source.
- When alreadyLightmapped is false, Obj1 and the background, which have lightmapped data, look fine. But Obj2 and Obj3 which should be realtime lit appear darker
- When alreadyLightmapped is true again, the background and obj1, which HAVE lightmapped data appear overexposed, being lit realtime And through lightmap. Obj2 and obj3 appear normal.