Save training `dtype` as part of the configuration

[pcuenca]

It'd be interesting to know the type that was used to train. However, as pointed out by @patrickvonplaten and @patil-suraj:

• It needs to be saved as a string; jnp.bfloat16 etc. cannot be serialized.
• We need to decide the naming to make it clear what it means.

Context: #565 (comment)

[patrickvonplaten]

Thanks for opening this issue - let's keep it in mind when improving JAX over time (once the Google colab problem is solved)

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the contributing guidelines are likely to be ignored.