Create a constellation_traits crate (#36088)

This change creates a `constellation_traits` crate. Previously messages
to the `Constellation` were in the `compositing_traits` crate, which
came about organically. This change moves these to a new crate which
also contains data types that are used in both compositing/libservo and
script (ie types that cross the process boundary). The idea is similar
to `embedding_traits`, but this is meant for types not exposed to the
API.

This change allows deduplicating `UntrustedNodeAddress`, which
previously had two versions to avoid circular dependencies.

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

components/webdriver_server/actions.rs

@@ -6,7 +6,7 @@ use std::collections::HashSet;
 use std::time::{Duration, Instant};
 use std::{cmp, thread};
 
-use compositing_traits::ConstellationMsg;
+use constellation_traits::ConstellationMsg;
 use embedder_traits::{MouseButtonAction, WebDriverCommandMsg, WebDriverScriptCommand};
 use ipc_channel::ipc;
 use keyboard_types::webdriver::KeyInputState;