Update cesium-native

[lilleyse]

We're on a fairly old commit of cesium-native #9599084.

In order to upgrade we need to:

• Update to C++ 20. Previously this wasn't possible due to an issue in one of the carbonite headers. See if this is fixed in Kit 107
• Fix Remove _DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR  #727 so that we don't need a custom cesium-native branch