Decouple Lights from Toggleable Visuals (and headphone music notes bugfix) (#35341)

* - Combine enum keys `ToggleableLightVisuals` and `ToggleVisuals` into `ToggleableVisuals`
- Rename `ToggleableLightVisualsComponent` to `ToggleableVisualsComponent` and `ToggleableLightVisualsSystem` to `ToggleableVisualsSystem`
  - (The `SpriteLayer` field on the component is now required because the old default of `light` doesn't make sense anymore)
- Make it so that `ToggleableVisualsComponent` works even when there's not a light attached to the entity
  - (Amazingly this seems to have only applied to  Headphones, but I can only imagine there are many other things people would like to do with simple toggleable visuals)
- Explicitly make `ItemTogglePointLightComponent`'s purpose to make `ToggleVisualsComponent` apply to `PointLightComponent`s on the same entity.
  - Add field `ToggleableVisualsColorModulatesLights`, which makes the `Color` appearance value of `ToggleableVisuals` modulate the color of lights on the same entity
  - Lots of prototype updates to uptake the above

* fix bad merge

* unbork robust

* blindly letting rider reformat stuff

* I guess I never cleaned up these imports at all

Content.Shared/Toggleable/ToggleActionEvent.cs

@@ -15,8 +15,24 @@ public sealed partial class ToggleActionEvent : InstantActionEvent;
 ///     Generic enum keys for toggle-visualizer appearance data & sprite layers.
 /// </summary>
 [Serializable, NetSerializable]
-public enum ToggleVisuals : byte
+public enum ToggleableVisuals : byte
 {
-    Toggled,
-    Layer
+    Enabled,
+    Layer,
+    Color,
+}
+
+/// <summary>
+///     Generic sprite layer keys.
+/// </summary>
+[Serializable, NetSerializable]
+public enum LightLayers : byte
+{
+    Light,
+
+    /// <summary>
+    ///     Used as a key for generic unshaded layers. Not necessarily related to an entity with an actual light source.
+    ///     Use this instead of creating a unique single-purpose "unshaded" enum for every visualizer.
+    /// </summary>
+    Unshaded,
 }