libservo: Move size handling to RenderContext from WindowMethods (#35621)

This is the first step toward removing `WindowMethods`, which will
gradually be integrated into the `WebView` and `WebViewDelegate`. Sizing
of the `WebView` is now handled by the a size associated with a
`RenderingContext`. `WebView`s will eventually just paint the entire
size of their `RenderingContext`. Notes:

- This is transitionary step so now there is a `WebView::resize` and a
  `WebView::move_resize`. The first is the future which will resize the
  `WebView` and its associated `RenderingContext`. The second is a
  function that the virtual `WebView`s that will soon be replaced by a
  the one-`WebView` per `WebView` model.
- We do not need to call `WebView::move_resize` at as much any longer
  because the default size of the `WebView` is to take up the whole
  `RenderingContext`.
- `SurfmanRenderingContext` is no longer exposed in the API, as a
  surfman context doesn't naturally have a size unless a surface is
  bound to it.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

Cargo.lock

@@ -1038,6 +1038,7 @@ dependencies = [
  "bitflags 2.8.0",
  "compositing_traits",
  "crossbeam-channel",
+ "dpi",
  "embedder_traits",
  "euclid",
  "fnv",
@@ -4342,6 +4343,7 @@ dependencies = [
  "crossbeam-channel",
  "devtools",
  "devtools_traits",
+ "dpi",
  "embedder_traits",
  "env_logger 0.10.2",
  "euclid",