Allow arbitrary val check intervals when using max_steps

[monney]

🚀 Feature

Currently when using the max epochs setting we can set val_check_interval to any arbitrary value we like. We cannot do this if max_steps is set. It must be less than one epoch.

Motivation

Constraining this value to be determined as a number of steps and also be less than an epoch makes it difficult to configure this value ahead of runtime, because an epoch length depends on many different factors. I usually use max_steps to easily configure schedulers and such that are stepped on a per batch basis, it allows values to be set before runtime in a portable way.

Pitch

allow this value to be any step count independent of epochs.

Alternatives

allow it to be defined a multiplier as when max_epochs is used

[monney]

Was used old API