Move ScriptToConstellationMsg to constellation_traits (#36364)

This is the last big change necessary to create the
`constellation_traits` crate. This moves the data structure for messages
that originate from the `ScriptThread` and are sent to the
`Contellation` to `constellation_traits`, effectively splitting
`script_traits` in half. Before, `script_traits` was responsible for
exposing the API of both the `ScriptThread` and the `Constellation` to
the rest of Servo.

- Data structures that are used by `ScriptToConstellationMsg` are moved
  to `constellation_traits`. The dependency graph looks a bit like this:
  `script_layout_interface` depends on `script_traits` depends on
  `constellation_traits` depends on `embedder_traits`.
- Data structures that are used in the embedding layer
  (`UntrustedNodeAddress`, `CompositorHitTestResult`, `TouchEventResult`
  and `AnimationState`) are moved to embedder_traits, to avoid a
  dependency cycle between `webrender_traits` and
  `constellation_traits`.
- Types dealing with MessagePorts and serialization are moved to
  `constellation_traits::message_port`.

Testing: This is covered by existing tests as it just moves types
around.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/script/dom/workletglobalscope.rs

@@ -5,6 +5,7 @@
 use std::sync::Arc;
 
 use base::id::PipelineId;
+use constellation_traits::{ScriptToConstellationChan, ScriptToConstellationMessage};
 use crossbeam_channel::Sender;
 use devtools_traits::ScriptToDevtoolsControlMsg;
 use dom_struct::dom_struct;
@@ -14,7 +15,7 @@ use js::rust::Runtime;
 use net_traits::ResourceThreads;
 use net_traits::image_cache::ImageCache;
 use profile_traits::{mem, time};
-use script_traits::{Painter, ScriptToConstellationChan, ScriptToConstellationMessage};
+use script_traits::Painter;
 use servo_url::{ImmutableOrigin, MutableOrigin, ServoUrl};
 use stylo_atoms::Atom;