Map dimensions are incorrect when shadow root is present

Nobody has claimed this yet.

It seems [`_updateContainerDimensions`](https://github.com/mapbox/mapbox-gl-js/blob/596da6b8e6bf4ff2530e82fce7edefb4aea33a17/src/ui/map.ts#L3993) function is implemented in such a way that if the map is placed inside the Shadow DOM, and the scaling transformation is applied outside of shadow root, then calculated canvas size will be incorrect.

Reproduction:
https://jsbin.com/kuxaveliri/1/edit?html,output

Note that the dimensions of the map inside the `#container` are halved because there is a scaling transform on the `body`.
We found a hot fix for our case, that seems to be working correctly (it is also attached in the repro above):

```js
map._updateContainerDimensions = function () {
if (!this._container) return

const width = this._container.offsetWidth || 400
const height = this._container.offsetHeight || 300

this._containerWidth = width
this._containerHeight = height
}
```

**mapbox-gl-js version**: 3.8.0

**browser**: Firefox 133.0, Chrome 131.0.6778.86

### Steps to Trigger Behavior

1. Place a map inside the shadow DOM
2. Apply CSS transform outside of the shadow root
3. Observe the map is scaled incorrectly, resulting in the doubled scaling factor.

### Link to Demonstration

https://jsbin.com/kuxaveliri/1/edit?html,output

### Expected Behavior

The map fully occupies the scaled `#container`, no matter if the shadow DOM is used or not.

### Actual Behavior

If the shadow DOM is present, the map is scaled incorrectly.

Start in src/ui/map.ts at _updateContainerDimensions and reproduce the behavior using the linked JSBin, comparing a map inside and outside a shadow root with the body transform applied. Verify the container and canvas dimensions against the expected scaled #container size, and confirm the map fully occupies it in both cases.

Written by the indexing model from the issue text.