Fix GPU bucket picker - not all necessary buckets are always present on GPU

[MichaelBuessemeyer]

Context

When having rotations active, it is possible to have an orientation in combination with the position where not all voxel that should be rendered are present on the GPU because the bucket picker does not pick the required bucket. This leads to black lines being rendered or a bucket of higher magnification, leading to blurred data being rendered.

Expected Behavior

The bucket picker should put all required buckets on the GPU avoiding rendering black or lower res data.

Current Behavior

There is a black line :D

Steps to Reproduce the bug

Might not work:

1. open l4_sample
2. Only view XY & 3d viewport
3. view #3593,3523,1006,0,0.701,30,0,0,50
4. (hopefully) see black line on the screen

The scenario described above with the visulization of bucket on GPU turned on.

If you rotate the 3d viewport a little to inspect whether all parts of the plane have a bucket on the GPU, the side view shows that's not the case at the exact location where the black line is.

Your Environment for bug

• Shouldn't matter