Read amplification upon checkpoint read
**Describe the bug**

NeMo currently executes load_checkpoint independently on all ranks, causing unnecessarily high filesystem reading. In contrast,
save_checkpoint functionality for nlp models is only executed on rank 0 / data_parallel_rank == 0: https://github.com/NVIDIA/NeMo/blob/ac50e5963ca4e23b7fd758f0732f6ed51200cc1d/nemo/collections/nlp/parts/nlp_overrides.py#L164-L171

**Steps/Code to reproduce bug**

See

https://github.com/NVIDIA/NeMo/blob/ac50e5963ca4e23b7fd758f0732f6ed51200cc1d/nemo/collections/nlp/parts/nlp_overrides.py#L195-L200

**Expected behavior**

Checkpoint is only read from filesystem on rank 0 / data_parallel_rank == 0 and broadcasted to all other ranks.