A Study Evaluating Safety and Efficacy of Obinutuzumab, Polatuzumab Vedotin (Pola), and Atezolizumab (Atezo) in Participants With Relapsed or Refractory Follicular Lymphoma (FL) and Rituximab, Atezo, and Pola in Participants With Relapsed or Refractory Diffuse Large B-Cell Lymphoma (DLBCL)