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`.

2 files changed, 3 insertions, 3 deletions

diff --git a/components/metrics/Cargo.toml b/components/metrics/Cargo.toml
index 08701edf372..888fabc2dd6 100644
--- a/components/metrics/Cargo.toml
+++ b/components/metrics/Cargo.toml
@@ -11,12 +11,12 @@ name = "metrics"
 path = "lib.rs"
 
 [dependencies]
+base = { workspace = true }
 gfx_traits = { workspace = true }
 ipc-channel = { workspace = true }
 log = { workspace = true }
 malloc_size_of = { workspace = true }
 malloc_size_of_derive = { workspace = true }
-msg = { workspace = true }
 profile_traits = { workspace = true }
 script_traits = { workspace = true }
 servo_config = { path = "../config" }
diff --git a/components/metrics/lib.rs b/components/metrics/lib.rs
index 7aa42f365ae..3effde8cac0 100644
--- a/components/metrics/lib.rs
+++ b/components/metrics/lib.rs
@@ -7,11 +7,11 @@ use std::cmp::Ordering;
 use std::collections::HashMap;
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
-use gfx_traits::Epoch;
+use base::id::PipelineId;
+use base::Epoch;
 use ipc_channel::ipc::IpcSender;
 use log::warn;
 use malloc_size_of_derive::MallocSizeOf;
-use msg::constellation_msg::PipelineId;
 use profile_traits::time::{send_profile_data, ProfilerCategory, ProfilerChan, TimerMetadata};
 use script_traits::{ConstellationControlMsg, LayoutMsg, ProgressiveWebMetricType};
 use servo_config::opts;