layout: Report memory usage for fragment and box trees. (#36553)

Add memory reporter integration for the fragment and box trees that are
persisted in the layout thread.

Testing: Looked at the numbers for https://servo.org and
https://html.spec.whatwg.org/. The former was very small, but the latter
was 700mb.

---------

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

Cargo.lock

@@ -1134,11 +1134,13 @@ dependencies = [
  "image",
  "ipc-channel",
  "log",
+ "malloc_size_of_derive",
  "pixels",
  "profile_traits",
  "raw-window-handle",
  "serde",
  "servo_geometry",
+ "servo_malloc_size_of",
  "strum_macros",
  "stylo",
  "stylo_traits",
@@ -4162,6 +4164,7 @@ dependencies = [
  "ipc-channel",
  "itertools 0.13.0",
  "log",
+ "malloc_size_of_derive",
  "net_traits",
  "num-traits",
  "parking_lot",
@@ -4174,6 +4177,7 @@ dependencies = [
  "servo_arc",
  "servo_config",
  "servo_geometry",
+ "servo_malloc_size_of",
  "servo_url",
  "stylo",
  "stylo_traits",
@@ -6822,6 +6826,7 @@ version = "0.0.1"
 dependencies = [
  "accountable-refcell",
  "app_units",
+ "atomic_refcell",
  "content-security-policy",
  "crossbeam-channel",
  "euclid",
@@ -6837,8 +6842,11 @@ dependencies = [
  "stylo",
  "stylo_dom",
  "stylo_malloc_size_of",
+ "taffy",
  "thin-vec",
  "tokio",
+ "unicode-bidi",
+ "unicode-script",
  "url",
  "uuid",
  "webrender_api",