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/constellation/tracing.rs

@@ -239,7 +239,7 @@ mod from_script {
                 Self::StopGamepadHapticEffect(..) => target_variant!("StopGamepadHapticEffect"),
                 Self::ShutdownComplete => target_variant!("ShutdownComplete"),
                 Self::ShowNotification(..) => target_variant!("ShowNotification"),
-                Self::ShowSelectElementMenu(..) => target_variant!("ShowSelectElementMenu"),
+                Self::ShowFormControl(..) => target_variant!("ShowFormControl"),
                 Self::FinishJavaScriptEvaluation(..) => {
                     target_variant!("FinishJavaScriptEvaluation")
                 },