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/shared/script/script_msg.rs

@@ -54,9 +54,9 @@ pub enum TouchEventResult {
     DefaultPrevented(TouchSequenceId, TouchEventType),
 }
 
-/// Messages from the script to the constellation.
+/// Messages sent from the `ScriptThread` to the `Constellation`.
 #[derive(Deserialize, IntoStaticStr, Serialize)]
-pub enum ScriptMsg {
+pub enum ScriptToConstellationMessage {
     /// Request to complete the transfer of a set of ports to a router.
     CompleteMessagePortTransfer(MessagePortRouterId, Vec<MessagePortId>),
     /// The results of attempting to complete the transfer of a batch of ports.
@@ -219,7 +219,7 @@ pub enum ScriptMsg {
     ReportMemory(IpcSender<MemoryReportResult>),
 }
 
-impl fmt::Debug for ScriptMsg {
+impl fmt::Debug for ScriptToConstellationMessage {
     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
         let variant_string: &'static str = self.into();
         write!(formatter, "ScriptMsg::{variant_string}")