If you surround 2x2 area of hemlock saplings with a ring of torches, the tree won't grow. We should probably make roots be placed by a tree decorator instead.

This is actually a bug in vanilla: https://bugs.mojang.com/browse/MC-8187

It's caused by the growth check in TreeFeature not accounting for 2x2 logs. Thus, we use a TwoLayersFeatureSize with a lower radius of 1, which checks a 3x3 area, as opposed to a radius of 0, which checks a 1x1 area. There is no way to make TreeFeature only check a 2x2 area at the base of the trunk.