Hotplate overhaul (#17586)

* Hotplate overhaul

- Beakers are now placed on top of the hotplate instead of itemslot.
- Hotplate LED now only lights up if it's heating something.
- More comments/xmldoc.
- Some other minor tweaks.

* Actually remove the beaker slot

Content.Server/Chemistry/Components/ActiveSolutionHeaterComponent.cs

@@ -3,5 +3,4 @@
 [RegisterComponent]
 public sealed class ActiveSolutionHeaterComponent : Component
 {
-
 }