Not all sendNodes for communication after fine to coarse were found.
This was only a problem when cutting the domain in the z-direction.

Avoid calling method to find neighborNodes in every timestep

Remove them from LevelGridBuilder

(cherry picked from commit 3191433948c45d04b49729cc92e9b54796981a7f)

* move cudaEventRecord to UpdateGrid27
* use variables for stream indices in UpdateGrid27
* create and destroy streams in Simulation.init() and Simulation.free()

Previously, the event was also triggered when data was written. This behavior caused crashes of VF

Thh new behaviour can turned off by passing false for the "onlyBulk" bool