add Trainer states

[Borda]

🚀 Feature

Add trainer states so in each time user get info what is happening

Motivation

simplify the return values and clean up the interface

Pitch

The state will be implemented as enum and updated according to Trainer phase:

• INITIALIZE
• RUNNING
• FINISHED
• TEARING_DOWN
• TERMINATED
• ...

[github-actions]

Hi! thanks for your contribution!, great first issue!

[zerogerc]

As I understood it right, the change is to add enum with phases, add corresponding updates, and logging of the current phase. @Borda I can take it as my first issue.

[Borda]

@zerogerc cool, that it adds an enum (with possible texts) and change the states according to the training phase...
if you need anything, just ping me on slack 🐰

[awaelchli]

Don't we want to control these states with decorators? I think having the code for these state changes mixed with the core training logic is a bit distracting and fragile, don't you think?

[Borda]

Don't we want to control these states with decorators? I think having the code for these state changes mixed with the core training logic is a bit distracting and fragile, don't you think?

well, decorators would be nicer :] @awaelchli mind comment/suggest on the open PR?