GPU/Cluster free way of converting checkpoints to HF

[terrykong]

From #99
https://github.com/NVIDIA/reinforcer/pull/99/files#r2027368058

[ashors1]

Solution provided in #185, but leaving this issue open since we'd like to make the conversion more efficient

[terrykong]

i'll close and create a new issue for the efficiency since technically #185 solves