script: Report associated memory for webgl objects (#42570)

As started in https://github.com/servo/servo/issues/42168 let's report
memory pressure for webgl objects. CanvasContexts report memory twice:
once because of underlying texture object and once by themself, but
that's okay as we also need to account for swapchain textures.

Computing exact size would be to much work and code so we report rough
estimations.

Testing: None

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>

components/script/dom/webgl/webglvertexarrayobject.rs

@@ -14,7 +14,7 @@ use crate::dom::webgl::webglobject::WebGLObject;
 use crate::dom::webgl::webglrenderingcontext::{Operation, WebGLRenderingContext};
 use crate::script_runtime::CanGc;
 
-#[dom_struct]
+#[dom_struct(associated_memory)]
 pub(crate) struct WebGLVertexArrayObject {
     webgl_object_: WebGLObject,
     array_object: VertexArrayObject,