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`.

1 files changed, 4 insertions, 4 deletions

diff --git a/components/script/dom/globalscope.rs b/components/script/dom/globalscope.rs
index 32febf8ab8e..7586a58793e 100644
--- a/components/script/dom/globalscope.rs
+++ b/components/script/dom/globalscope.rs
@@ -14,6 +14,10 @@ use std::thread::JoinHandle;
 use std::time::Instant;
 use std::{mem, ptr};
 
+use base::id::{
+    BlobId, BroadcastChannelRouterId, MessagePortId, MessagePortRouterId, PipelineId,
+    ServiceWorkerId, ServiceWorkerRegistrationId,
+};
 use content_security_policy::CspList;
 use crossbeam_channel::Sender;
 use devtools_traits::{PageError, ScriptToDevtoolsControlMsg};
@@ -34,10 +38,6 @@ use js::rust::{
     MutableHandleValue, ParentRuntime, Runtime,
 };
 use js::{JSCLASS_IS_DOMJSCLASS, JSCLASS_IS_GLOBAL};
-use msg::constellation_msg::{
-    BlobId, BroadcastChannelRouterId, MessagePortId, MessagePortRouterId, PipelineId,
-    ServiceWorkerId, ServiceWorkerRegistrationId,
-};
 use net_traits::blob_url_store::{get_blob_origin, BlobBuf};
 use net_traits::filemanager_thread::{
     FileManagerResult, FileManagerThreadMsg, ReadFileProgress, RelativePos,