Support restarting a ParaView time-series from a checkpoint

Support restarting a ParaView time-series from a checkpoint: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). When a transient simulation writes its output through MFEM's ParaView data collection, each call to Save() appends one time-step entry to the collection's…