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/shared/embedder/Cargo.toml

@@ -11,13 +11,13 @@ name = "embedder_traits"
 path = "lib.rs"
 
 [dependencies]
+base = { workspace = true }
 cfg-if = { workspace = true }
 crossbeam-channel = { workspace = true }
 ipc-channel = { workspace = true }
 keyboard-types = { workspace = true }
 lazy_static = { workspace = true }
 log = { workspace = true }
-msg = { workspace = true }
 num-derive = "0.4"
 num-traits = { workspace = true }
 serde = { workspace = true }

components/shared/embedder/lib.rs

@@ -6,11 +6,11 @@ pub mod resources;
 
 use std::fmt::{Debug, Error, Formatter};
 
+use base::id::{PipelineId, TopLevelBrowsingContextId, WebViewId};
 use crossbeam_channel::{Receiver, Sender};
 use ipc_channel::ipc::IpcSender;
 use keyboard_types::KeyboardEvent;
 use log::warn;
-use msg::constellation_msg::{InputMethodType, PipelineId, TopLevelBrowsingContextId, WebViewId};
 use num_derive::FromPrimitive;
 use serde::{Deserialize, Serialize};
 use servo_url::ServoUrl;
@@ -368,3 +368,23 @@ pub enum PermissionRequest {
     Granted,
     Denied,
 }
+
+/// Used to specify the kind of input method editor appropriate to edit a field.
+/// This is a subset of htmlinputelement::InputType because some variants of InputType
+/// don't make sense in this context.
+#[derive(Debug, Deserialize, Serialize)]
+pub enum InputMethodType {
+    Color,
+    Date,
+    DatetimeLocal,
+    Email,
+    Month,
+    Number,
+    Password,
+    Search,
+    Tel,
+    Text,
+    Time,
+    Url,
+    Week,
+}