Fully support <input type=color> (#36992)

This change adds a shadow-tree widget for `<input type=color>` elements.
It also involves some changes to the way layout interacts with the DOM,
because currently all `input` and `textarea` elements are rendered as
plain text and their descendants are ignored. This obviously doesn't
work for `<input type={color, date, range, etc}>`.


![image](https://github.com/user-attachments/assets/4f16c3b0-1f79-4095-b19d-1153f5853dd5)

<details><summary>HTML used for the screenshot above</summary>

```html
<input type=color>
```

</details>



Testing: I doubt that this affects WPT tests, because the appearance and
behaviour of the widget is almost entirely unspecified.

---------

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

components/script/dom/htmlselectelement.rs

@@ -14,7 +14,7 @@ use style::attr::AttrValue;
 use stylo_dom::ElementState;
 use embedder_traits::{SelectElementOptionOrOptgroup, SelectElementOption};
 use euclid::{Size2D, Point2D, Rect};
-use embedder_traits::EmbedderMsg;
+use embedder_traits::{FormControl as EmbedderFormControl, EmbedderMsg};
 
 use crate::dom::bindings::codegen::GenericBindings::HTMLOptGroupElementBinding::HTMLOptGroupElement_Binding::HTMLOptGroupElementMethods;
 use crate::dom::activation::Activatable;
@@ -406,12 +406,10 @@ impl HTMLSelectElement {
         let selected_index = self.list_of_options().position(|option| option.Selected());
 
         let document = self.owner_document();
-        document.send_to_embedder(EmbedderMsg::ShowSelectElementMenu(
+        document.send_to_embedder(EmbedderMsg::ShowFormControl(
             document.webview_id(),
-            options,
-            selected_index,
             DeviceIntRect::from_untyped(&rect.to_box2d()),
-            ipc_sender,
+            EmbedderFormControl::SelectElement(options, selected_index, ipc_sender),
         ));
 
         let Ok(response) = ipc_receiver.recv() else {