Starlight colors with parallax, small parallax code clean-up (#77020)

The space gas parallax now colors starlight in the color of the gas: 


![image](https://github.com/tgstation/tgstation/assets/7501474/18b5554f-6357-473e-8f43-64aad1517be0)

<details>
  <summary>Others</summary>
  

![image](https://github.com/tgstation/tgstation/assets/7501474/1599795f-f76d-479d-a1c3-aa19390ad403)

![image](https://github.com/tgstation/tgstation/assets/7501474/fb992df0-ee85-4afc-a546-f28e739ea923)

![image](https://github.com/tgstation/tgstation/assets/7501474/ed64a01c-c104-4177-bf63-b82288251aa9)

</details>

I also cleaned up parallax random code a bit, making it easier to add
new parallaxes and add minor effects to them

The radioactive nebula parallax thing has also been moved to SSparallax
to make it easier and a bit more sane to change

🆑
add: Starlight will color with space gas parallax
code: Cleans up random parallax code / radioactive nebula parallax code
/🆑

## Why it's good for the game

We can change the starlight color now (mostly thanks to @LemonInTheDark
making light code easier to work with), so I thought it'd be fun to
actually do! If people hate it, I'll turn it off and we can just call
this a code clean-up PR

code/controllers/subsystem/processing/station.dm

@@ -21,6 +21,7 @@ PROCESSING_SUBSYSTEM_DEF(station)
 	#endif
 
 	announcer = new announcer() //Initialize the station's announcer datum
+	SSparallax.random_layer.apply_global_effects() //Apply station effects that parallax might have
 
 	return SS_INIT_SUCCESS