LRs updates are called at the end of a skipped epoch (#21307)
* fix: Update lr if train_batch_start returns -1
* fix: Rename variable: should_skip_rest_of_epoch
* chore: Update changelog
* fix: Batch increment
* Apply suggestion from @SkafteNicki
* test: Check lr is updated at the end of epoch
When `on_train_batch_start` returns -1, the rest of the epoch is skipped.
The lr update should still happen at the end of the epoch.
- Test is_last_batch has been set correctly
- Test lr has been updated at the end of each epoch
* doc: Add documentation for lr update
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Co-authored-by: Nicki Skafte Detlefsen <skaftenicki@gmail.com>