Implements shared particle holders, re-adds slimed status particles using the new system (#87892)

## About The Pull Request

Partial revert of #86701
Implements a shared holder particle system, somewhat inspired by
https://github.com/Baystation12/Baystation12/pull/34014 (thanks Kapu).
Atoms can be assigned "shared" particles via add_shared_particles, with
an optional "alternate" key passed as a second arg if you're planning to
edit the returned particle holder (for example, color it like slimed
status does). Removing is done via remove_shared_particles with an
option to delete the shared holder if nothing is using it anymore (on by
default). This system should be prioritized over normal particle holders
when a lot of entities would be using a certain particle effect (like
fires) as it conserves a lot of clientside performance.

Burning, acid, decaying, firestacks and slimed status now use this
system which should help with clientside performance and amount of atoms
created/destroyed.

## Why It's Good For The Game

Less clientside lag.

## Changelog
🆑
refactor: Firestacks, burning/acid/decaying effects and (brought back
after being temporarily removed) slimed status effects now use a new
"shared" particles system, which should considerably improve client
performance when encountering a lot of burning/slimed entities.
/🆑

---------

Co-authored-by: Ghom <42542238+Ghommie@users.noreply.github.com>

code/game/objects/effects/particles/fire.dm

@@ -34,6 +34,9 @@
 	spin = generator(GEN_NUM, list(-15,15), NORMAL_RAND)
 	scale = generator(GEN_VECTOR, list(0.5,0.5), list(2,2), NORMAL_RAND)
 
+/particles/embers/minor
+	spawning = 1
+
 /particles/embers/spark
 	count = 3
 	spawning = 2