Replace all uses of the heapsize crate with malloc_size_of.

Servo currently uses `heapsize`, but Stylo/Gecko use `malloc_size_of`.
`malloc_size_of` is better -- it handles various cases that `heapsize` does not
-- so this patch changes Servo to use `malloc_size_of`.

This patch makes the following changes to the `malloc_size_of` crate.

- Adds `MallocSizeOf` trait implementations for numerous types, some built-in
  (e.g. `VecDeque`), some external and Servo-only (e.g. `string_cache`).

- Makes `enclosing_size_of_op` optional, because vanilla jemalloc doesn't
  support that operation.

- For `HashSet`/`HashMap`, falls back to a computed estimate when
  `enclosing_size_of_op` isn't available.

- Adds an extern "C" `malloc_size_of` function that does the actual heap
  measurement; this is based on the same functions from the `heapsize` crate.

This patch makes the following changes elsewhere.

- Converts all the uses of `heapsize` to instead use `malloc_size_of`.

- Disables the "heapsize"/"heap_size" feature for the external crates that
  provide it.

- Removes the `HeapSizeOf` implementation from `hashglobe`.

- Adds `ignore` annotations to a few `Rc`/`Arc`, because `malloc_size_of`
  doesn't derive those types, unlike `heapsize`.

components/style/values/animated/color.rs

@@ -11,7 +11,7 @@ use values::distance::{ComputeSquaredDistance, SquaredDistance};
 ///
 /// Unlike in computed values, each component value may exceed the
 /// range `[0.0, 1.0]`.
-#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
 #[derive(Clone, Copy, Debug, PartialEq, ToAnimatedZero)]
 pub struct RGBA {
     /// The red component.
@@ -70,7 +70,7 @@ impl ComputeSquaredDistance for RGBA {
 }
 
 #[allow(missing_docs)]
-#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub struct Color {
     pub color: RGBA,

components/style/values/animated/effects.rs

@@ -28,7 +28,7 @@ pub type TextShadowList = ShadowList<SimpleShadow>;
 /// An animated value for shadow lists.
 ///
 /// <https://drafts.csswg.org/css-transitions/#animtype-shadow-list>
-#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
 #[derive(Clone, Debug, PartialEq)]
 pub struct ShadowList<Shadow>(Vec<Shadow>);
 
@@ -36,7 +36,7 @@ pub struct ShadowList<Shadow>(Vec<Shadow>);
 pub type BoxShadow = GenericBoxShadow<Option<RGBA>, Length, NonNegativeLength, Length>;
 
 /// An animated value for the `filter` property.
-#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
 #[derive(Clone, Debug, PartialEq)]
 pub struct FilterList(pub Vec<Filter>);