fix X-axis face occlusion

[KaptainWutax]

This is a very small issue affecting more detailed builds but the occlusion check is flipped. Other functions use (1 - side) which is correct but not generateXOuterOpaqueGeometry.

Before:

After:

[MCRcortex]

<3 there are so many missing occlusion checks in the factory
(place down scaffolding) and culling against non full blocks is entirly missing (e.g. between snow layers)

[KaptainWutax]

I can slowly chip away at some the easier ones if you want! I'm also noticing a few inconsistencies between inner and outer occlusion since I'm placing some builds aligned with the 32x32x32 grid.