Save model data in half precision (bf16) and load back to the full precision f32

[antimora]

Feature description

A user should be able to specify if the model data should be saved in half precision, and tell if the data should be loaded back to the full precision

Feature motivation

Often the performance of model inference does not degrade much if f32 precision is truncated in half but it may matter during training. To reduce the size of the exported model, it would be beneficial to save in bf16 (truncated version of f32) and later to load back in f32 (If the target architecture supports only f32 and up).

(Optional) Suggest a Solution

Use half library to convert f32 to bf16. half also supports serde for (de)serialization. User should be able to specify target data (f32).