Per-view `maximumScreenSpaceError`

It would be nice if `maximumScreenSpaceError` could be configured per-view, e.g. `16` in one viewport and `64` in another viewport that requires less detail.

A few ways this could be implemented (just rough notes):

* `Tileset` provides a `maximumScreenSpaceError` for each view state
* `ViewState` has a `maximumScreenSpaceErrorMultiplier`

Option 2 is less flexible but probably cleaner to implement. Though one might be able to scale the `viewportSize` and get a similar effect.

This was suggested on the [community forum](https://community.cesium.com/t/keeping-cesium-tiles-loaded-around-a-moving-sensor-platform-while-user-navigates-freely-dual-viewport-workaround-performance-cost/46520).

Start by reviewing the existing Tileset and ViewState entry points mentioned in the issue, then compare the per-Tileset and per-ViewState approaches. Done means each viewport can use its own maximumScreenSpaceError, including the example values 16 and 64, without changing the other view.

Written by the indexing model from the issue text.