[MAPS3D-1933] Allow specifying ground shadow draw position in layer stack (#8631)

Fixes https://mapbox.atlassian.net/browse/MAPS3D-1933
Fixes https://mapbox.atlassian.net/browse/MAPS3D-2090

Add new property `shadow-draw-before-layer` to the directional light.
When terrain is disabled and the layer is specified, shadows are drawn
to the ground before the specified layer. This allows customers to fix
issues like shown in the image below. The problem is that the style has
shadow-casting layers after the middle slot, but moving the symbol layer
(or similar) to the top slot is not desirable. Existing behavior was to
always render the shadow to the ground after the last shadow-casting
layer, but this is not acceptable in some cases.

<img width="640" height="481" alt="image"
src="https://github.com/user-attachments/assets/fe5009fa-e69f-48b2-a947-d480d927917b"
/>

```
<public>
Add shadow-draw-before-layer property to directional light to allow specifying shadow draw order.
</public>
```

cc @mapbox/gl-js
cc @mapbox/gl-native
cc @mapbox/maps-ios
cc @mapbox/maps-android

cc @mapbox/sdk-ci

---------

Co-authored-by: Changelog autocreator bot <[email protected]>
(cherry picked from commit c69f78e0b6842a819468e2256335a600de8b58f8)
GitOrigin-RevId: 7d14f31cfb96e1df8796e09fc4e290a7bbf22fd2

Author: 2 people

CHANGELOG.md

@@ -7,7 +7,9 @@ Mapbox welcomes participation and contributions from everyone.
 ### ⚠️ Breaking changes
 * Remove line-cutout-width and change line-cutout-opacity default to 1.0
 
+### Features ✨ and improvements 🏁
 * Add Standard Style color and 3D configuration options: `colorBuildings`, `colorCommercial`, `colorEducation`, `colorIndustrial`, `colorLand`, `colorMedical`, `show3dBuildings`, `show3dFacades`, `show3dLandmarks`, and `show3dTrees`.
+* Add `shadowDrawBeforeLayer` property to directional light to allow specifying the position in the layer stack for drawing shadows on the ground.
 
 ## 11.17.0
 ## 11.17.0 - 04 December, 2025