Fix csg bunny

[rndexe]

1. Set precise={false} on Center. Not sure why this fixes the error, might be related to
   Box3: Better support for animated objects in expandByObject() in precise mode. mrdoob/three.js#26919 and a combination of csg mesh, it works fine on other meshes.

On further analysis the regression does appear in r158 of threejs where this change was made. Not sure if this counts as an edge case which was missed.

Default value in drei Center is precise = true

3. Fix AccumulativeShadows alphaTest and RandomizedLight intensity
4. Change Environment blur to backgroundBluriness

• ready to merge

[abernier]

is this one also ready?

[rndexe]

I'm not sure if this is an introduced bug in three in how it handles precise Box3.setFromObject calculations, or a bug in three-bvh-csg. But yeah the example is no longer broken if that's all that matters.