Avoid collision shapes outside world border in findFreePosition

This is to correctly adhere to Vanilla behavior.

patches/server/Moonrise-optimisation-patches.patch

@@ -31633,6 +31633,16 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +            null
 +        );
 +
++        final WorldBorder worldBorder = this.getWorldBorder();
++        if (worldBorder != null) {
++            aabbs.removeIf((final AABB aabb) -> {
++                return !worldBorder.isWithinBounds(aabb);
++            });
++            voxels.removeIf((final VoxelShape shape) -> {
++                return !worldBorder.isWithinBounds(shape.bounds());
++            });
++        }
++
 +        // push voxels into aabbs
 +        for (int i = 0, len = voxels.size(); i < len; ++i) {
 +            aabbs.addAll(voxels.get(i).toAabbs());