feature: Record batch time

[isamu-isozaki]

This piece of code helped me identify how much time is spent in the data processing stage, the forward pass, and backward pass so that I know where to optimize.
The main steps blocking this pr will be

• Figure out how to log with trainer since I think the def log function is not present currently because of refactoring

[isamu-isozaki]

I'm thinking if this can become a callback

[limiteinductive]

Thanks this is gonna be useful! Maybe you can take inspiration on how the TrainingClock Callback is implemented? Let's try to pollute as little as possible the core of the Trainer

[isamu-isozaki]

@limiteinductive do you think I should make a timer config or merge timer with clock?

[limiteinductive]

@limiteinductive do you think I should make a timer config or merge timer with clock?

I think it makes sense to merge with Clock and extend its config.