Improve visibility check in tileset traversal

[lilleyse]

This is a better way to set updateVisibilityFrame in the 3D Tiles traversal code which is used to limit the number of times a tile's visibility can be computed during each traversal.

The previous way had an edge case where the visibility frame would not get reset after a previous pass within the same frame if the tile's visibility was checked but it wasn't actually visited. This can happen with the cull-with-children-bounds optimization. I only hit this by calling pickFromRay after a pick, and it only happened sometimes.

• CHANGES.md

[cesium-concierge]

Thanks for the pull request @lilleyse!

• ✔️ Signed CLA found.
• ❔ CHANGES.md was not updated.
  • If this change updates the public API in any way, please add a bullet point to CHANGES.md.

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[lilleyse]

Updated CHANGES.md. I'm not really sure how to test this without going through a lot of trouble. In any case the behavior is nearly the same as before and all tests pass locally.

@ggetz can you review?

[ggetz]

Tested a few different tilesets with picking and behavior is the same, so I think this should be good to merge. Thanks @lilleyse !