Move non-gfx things out of gfx_traits and create a base crate (#32296)

For a long time, `gfx_traits` has held a lot of things unrelated to graphics
and also unrelated to the `gfx` crate (which is mostly about fonts).
This is a cleanup which does a few things:

1. Move non `gfx` crate things out of `gfx_traits`. This is important in
   order to prevent dependency cycles with a different integration between
   layout, script, and fonts.
2. Rename the `msg` crate to `base`. It didn't really contain anything
   to do with messages and instead mostly holds ids, which are used
   across many different crates in Servo. This new crate will hold the
   *rare* data types that are widely used.

Details:

 - All BackgroundHangMonitor-related things from base to a new
   `background_hang_monitor_api` crate.
 - Moved `TraversalDirection` to `script_traits`
 - Moved `Epoch`-related things from `gfx_traits` to `base`.
 - Moved `PrintTree` to base. This should be widely useful in Servo.
 - Moved `WebrenderApi` from `base` to `webrender_traits` and renamed it
   to `WebRenderFontApi`.

components/net/Cargo.toml

@@ -16,6 +16,7 @@ doctest = false
 [dependencies]
 async-recursion = "0.3.2"
 async-tungstenite = { workspace = true }
+base = { workspace = true }
 base64 = { workspace = true }
 brotli = "3"
 bytes = "1"
@@ -42,7 +43,6 @@ malloc_size_of = { workspace = true }
 malloc_size_of_derive = { workspace = true }
 mime = { workspace = true }
 mime_guess = { workspace = true }
-msg = { workspace = true }
 net_traits = { workspace = true }
 percent-encoding = { workspace = true }
 pixels = { path = "../pixels" }

components/net/http_loader.rs

@@ -9,6 +9,7 @@ use std::sync::{Arc as StdArc, Condvar, Mutex, RwLock};
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
 use async_recursion::async_recursion;
+use base::id::{HistoryStateId, PipelineId};
 use crossbeam_channel::Sender;
 use devtools_traits::{
     ChromeToDevtoolsControlMsg, DevtoolsControlMsg, HttpRequest as DevtoolsHttpRequest,
@@ -32,7 +33,6 @@ use hyper_serde::Serde;
 use ipc_channel::ipc::{self, IpcSender};
 use ipc_channel::router::ROUTER;
 use log::{debug, error, info, log_enabled, warn};
-use msg::constellation_msg::{HistoryStateId, PipelineId};
 use net_traits::pub_domains::reg_suffix;
 use net_traits::quality::{quality_to_value, Quality, QualityItem};
 use net_traits::request::Origin::Origin as SpecificOrigin;

components/net/tests/fetch.rs

@@ -11,6 +11,7 @@ use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::{Arc, Mutex, Weak};
 use std::time::{Duration, SystemTime};
 
+use base::id::TEST_PIPELINE_ID;
 use crossbeam_channel::{unbounded, Sender};
 use devtools_traits::{HttpRequest as DevtoolsHttpRequest, HttpResponse as DevtoolsHttpResponse};
 use headers::{
@@ -22,7 +23,6 @@ use http::header::{self, HeaderMap, HeaderName, HeaderValue};
 use http::{Method, StatusCode};
 use hyper::{Body, Request as HyperRequest, Response as HyperResponse};
 use mime::{self, Mime};
-use msg::constellation_msg::TEST_PIPELINE_ID;
 use net::fetch::cors_cache::CorsCache;
 use net::fetch::methods::{self, CancellationListener, FetchContext};
 use net::filemanager_thread::FileManager;

components/net/tests/http_cache.rs

@@ -2,9 +2,9 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use base::id::TEST_PIPELINE_ID;
 use http::header::{HeaderValue, EXPIRES};
 use http::StatusCode;
-use msg::constellation_msg::TEST_PIPELINE_ID;
 use net::http_cache::HttpCache;
 use net_traits::request::{Origin, Referrer, Request};
 use net_traits::response::{HttpsState, Response, ResponseBody};

components/net/tests/http_loader.rs

@@ -11,6 +11,7 @@ use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex, RwLock};
 use std::time::Duration;
 
+use base::id::TEST_PIPELINE_ID;
 use cookie_rs::Cookie as CookiePair;
 use crossbeam_channel::{unbounded, Receiver};
 use devtools_traits::{
@@ -29,7 +30,6 @@ use http::{Method, StatusCode};
 use hyper::{Body, Request as HyperRequest, Response as HyperResponse};
 use ipc_channel::ipc;
 use ipc_channel::router::ROUTER;
-use msg::constellation_msg::TEST_PIPELINE_ID;
 use net::cookie::Cookie;
 use net::cookie_storage::CookieStorage;
 use net::http_loader::determine_requests_referrer;