Support depthFailMaterial for clamped polylines

I couldn't find an issue on this, but it appears that depthFailMaterial is not support for polylines that are clamped to ground. This Sandcastle example works around this issue by not clamping the polyline to ground, and instead sampling the heights of the terrain:

https://sandcastle.cesium.com/index.html?src=Clamp%20to%20Terrain.html

(Click the "sample line positions" in the dropdown).

[Here's a version of this](https://sandcastle.cesium.com/index.html#c=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) that uses `clampToGround: true`. Notice depthFailMaterial has no effect and there is no warning or anything.

Is this just a matter of threading the depthFailAppearance down into `StaticGroundPolylinePerMaterialBatch.js` ? If there's a more fundamental reason why clamped polylines can't use depthFailMaterial we should issue a `oneTimeWarning` explaining that instead of silently failing.

Start with the linked Clamp to Terrain Sandcastle example and inspect StaticGroundPolylinePerMaterialBatch.js, especially how depthFailAppearance is handled for clamped polylines. Determine whether depthFailMaterial can be supported; done means it takes effect in the example, or a one-time warning clearly explains why it cannot.

Written by the indexing model from the issue text.