Update PipeRPCPlugin compatibility to pytorch 1.7.0+
🚀 Feature

Latest pytorch-lightning supports Sequential Model Parallelism, but compatible only with torch==1.6.0. Supporting 1.7.0+ allows us to exploit latest GPUs such as RTX 3000 series.

Motivation

Fine-tuning models too large for a single GPU.

Pitch

PipeRPCPlugin to support torch==1.7.0 or higher.

Alternatives

pl.Trainer supports accelerator='sharded' option without data-parallelism. (i.e. batch_size=1)

Additional context
N/A