constellation: Rename messages sent to the Constellation (#36341)

Messages that are sent to the `Constellation` have pretty ambiguous
names.
This change does two renames:

- `ConstellationMsg` → `EmbedderToConstellationMessage`
- `ScriptMsg` → `ScriptToConstellationMessage`

This naming reflects that the `Constellation` stands in between the
embedding layer and the script layer and can receive messages from both.
Soon both of these message types will live in `constellation_traits`,
reflecting the idea that the `_traits` variant for a crate is
responsible for exposing the API for that crate.

Testing: No new tests are necessary here as this just renames two enums.

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

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

components/script/dom/serviceworkercontainer.rs

@@ -8,7 +8,9 @@ use std::rc::Rc;
 use dom_struct::dom_struct;
 use ipc_channel::ipc;
 use ipc_channel::router::ROUTER;
-use script_traits::{Job, JobError, JobResult, JobResultValue, JobType, ScriptMsg};
+use script_traits::{
+    Job, JobError, JobResult, JobResultValue, JobType, ScriptToConstellationMessage,
+};
 
 use crate::dom::bindings::codegen::Bindings::ServiceWorkerContainerBinding::{
     RegistrationOptions, ServiceWorkerContainerMethods,
@@ -179,7 +181,7 @@ impl ServiceWorkerContainerMethods<crate::DomTypeHolder> for ServiceWorkerContai
         // B: Step 14: schedule job.
         let _ = global
             .script_to_constellation_chan()
-            .send(ScriptMsg::ScheduleJob(job));
+            .send(ScriptToConstellationMessage::ScheduleJob(job));
 
         // A: Step 7
         promise