`SampleTerrain` and `SampleTerrainMostDetailed` regression on thrown errors

[ggetz]

Historically, SampleTerrain and SampleTerrainMostDetailed would reject if a 404 error was thrown. At some point in time (I assume with https://github.com/CesiumGS/cesium/pull/10149), this behavior broke and a cartographic with undefined height is returned instead.

Sandcastle

To throw a bit of a wrench into the gears, https://github.com/CesiumGS/cesium/pull/11530 has since been added, unknowingly adding an opt-in flag to replicate the previous behavior.

We will likely remove or change the default for that flag and restore the older behavior where an error would cause the promise returned by the function to reject.