"GetStaticBatchElementShadowVisibility()" removed at engine 4.17 update

[xwev]

This leads to partial / incomplete shadows when using "GetStaticBatchElementVisibility()"
for the chunk backface culling (based on ViewPosition and FaceIndex)
(shadows incomplete due to culled faces not affecting lighting).

We can disable "bRequiresPerElementVisibility" to get the complete shadows,
but then we lose the large performance benefit of the culling.

Any recommendations?

commit reference:
https://github.com/EpicGames/UnrealEngine/commit/81ef7a206b58eb8204c9da4315aecd14cabde9c7#diff-0b08829a2ac94007500056981f30f153