Option for rendering at CSS pixels

[lilleyse]

Cesium 1.61 changed Cesium to render at device pixels rather than CSS pixels but there has been interest in going back to the old behavior. We should consider adding a property viewer.useBrowserRecommendedResolution that renders based on CSS pixels.

There was discussion about this in #8083 and now there seems to be sufficient demand:

• SSE Independent from Resolution Density & Cesium Renders at Screen Res #8083 (comment)
• SSE Independent from Resolution Density & Cesium Renders at Screen Res #8083 (comment)
• Use CSS pixel units everywhere #8113 (comment)

[lilleyse]

This will also include updating the Resolution Scale sandcastle