Surprisingly low performance on Android

Originally mentioned here:
https://community.cesium.com/t/very-laggy-on-android/25351/13

And confirmed myself. My Pixel 6 Pro averages 6-7 FPS when looking straight down at the ground with just Cesium World Terrain enabled. I would expect better performance than this, and I'm not sure why it's so low. We should investigate whether something major is tanking our performance on Android.

Reproduce the report on a Pixel 6 Pro with only Cesium World Terrain enabled, using the stated straight-down view and measuring the 6–7 FPS result. Profile the Android run to identify what is consuming frame time; done means a documented cause and a verified performance improvement or clear next action.

Written by the indexing model from the issue text.