Add a checkpoint averaging script for the new .distcp checkpoint format
This issue is stale because it has been open for 30 days with no activity. Remove stale label or comment or this will be closed in 7 days. This issue was closed because it has been inactive for 7 days since being marked as stale. This issue is stale because it has been open for 30 days with no activity. Remove stale label or comment or this will be closed in 7 days. would be great to address this
**Is your feature request related to a problem? Please describe.**

We found checkpoint averaging to be very helpful, but the current scripts in https://github.com/NVIDIA/NeMo/tree/main/scripts/checkpoint_averaging don't work with the new format. 

**Describe the solution you'd like**

Please provide an example of the averaging script that works.
