Allow a default lightPreset value

Nobody has claimed this yet.

## Motivation

Related to https://github.com/mapbox/mapbox-gl-js/issues/12841

Currently, setting the map theme is done after the style is loaded:

```js
map.on('style.load', () => {
map.setConfigProperty('basemap', 'lightPreset', 'night')
})
```

One issue with waiting for the style to load before setting the `lightPreset` value is that if you want a default 'night' then you get a flash of light gray `#f3f0ef` before it sets the colors for the 'night' style.
This flash of gray occurs on initial map load as well as when switching back and forth between styles e.g. satellite.

## Design Alternatives

The current workaround is to provide a full `style` hash while initializing the map:

```js
const map = new mapboxgl.Map({
center: [29, 29],
container: 'map',
minZoom: 1,
projection: 'mercator',
zoom: 1,
style: {
version: 8,
imports: [
{
id: 'basemap',
url: 'mapbox://styles/mapbox/standard',
config: {
lightPreset: 'night',
}
}
],
sources: {},
layers: []
}
})
```

If there's code in place that changes `lightPreset` to 'day' for some visitors (e.g. a site setting to choose day/night/system themes) then their version of the map will get a brief flash of a dark color, but it feels a bit less impactful than the reverse.
~~My main worry with this approach is whatever that `version` is, because changing it breaks the map. I'm unsure if the expectation of `8` is hard coded in the version of Mapbox GL JS in use, or if that's set/expected in a place independent of package updates.~~ The `version` is just [required to be 8](https://docs.mapbox.com/style-spec/reference/root/#version) 🤷

If `lightPreset` was a top-level configuration option on the Map (along with bearing, center, etc), the map could initially load in the chosen color theme and we wouldn't receive flashes of the opposite color.

## Design

### Mock-Up

```js
const map = new mapboxgl.Map({
center: [29, 29],
container: 'map',
minZoom: 1,
projection: 'mercator',
zoom: 1,
lightPreset: 'night'
})
```

### Concepts

### Implementation

🤷 I don't know enough of the internal code to know how to implement this or - to be fair - whether it's possible in the current state.

Start by tracing the map constructor options, style.load handling, and setConfigProperty('basemap', 'lightPreset', ...) behavior described in the issue. Determine whether a top-level lightPreset can be applied before the initial style renders and how it should behave when styles switch. Done means the initial map uses the requested preset without a flash of the opposite theme, with the relevant behavior covered by tests if existing coverage is found.

Written by the indexing model from the issue text.