The `BKE_bvhtree_from_pointcloud_get` function have requirements for
input point cloud argument and initialization of `BVHTreeFromPointCloud`
can be skipped. Due to `BVHTreeFromPointCloud` is not initialized by
default constructor, it can contains garbage data. To check if tree is
initialized field of `BVHTreeFromPointCloud`, return argument shouldn't
be ignored. `[[nodiscard]]` attributes is added.
Pull Request: https://projects.blender.org/blender/blender/pulls/109892