style: Remove dependency on servo_config (was #31409) (#31411)

* Initial style_config crate

* Remove servo_config from style

* Remove servo_config from tests/unit/style

* Plumb servo prefs into stylo

* Clean up dependencies

* Fix formatting

* Add unit tests

* Add comment about avoiding clone

* Fix bug where getters acquire unnecessary write lock

* Remove stray dbg!()

* Plumb default prefs into Stylo as well

* Add comments about logging and mapping new pref types

Cargo.lock

@@ -5396,6 +5396,7 @@ dependencies = [
  "servo_config_plugins",
  "servo_geometry",
  "servo_url",
+ "style_config",
  "url",
 ]
 
@@ -5781,12 +5782,12 @@ dependencies = [
  "serde",
  "servo_arc",
  "servo_atoms",
- "servo_config",
  "smallbitvec",
  "smallvec",
  "static_assertions",
  "static_prefs",
  "string_cache",
+ "style_config",
  "style_derive",
  "style_traits",
  "thin-vec",
@@ -5802,6 +5803,13 @@ dependencies = [
  "walkdir",
 ]
 
+[[package]]
+name = "style_config"
+version = "0.0.1"
+dependencies = [
+ "lazy_static",
+]
+
 [[package]]
 name = "style_derive"
 version = "0.0.1"
@@ -5827,7 +5835,6 @@ dependencies = [
  "serde_json",
  "servo_arc",
  "servo_atoms",
- "servo_config",
  "style",
  "style_traits",
  "url",