reset train dataloader after OOM

[veronicamorfi]

What does this PR do?

Fixes #9625
binsearch scaling in batch size scaling wasn't reseting the dataloader batchsize after an OOM error.
Calling the reset function for the train dataloader fixes that.

Does your PR introduce any breaking changes? If yes, please list them.

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[SkafteNicki]

Should there be a similar reset here for power scaling:
https://github.com/PyTorchLightning/pytorch-lightning/blob/ad32132c204ac9ee6003586e6ee44e2befa6db79/pytorch_lightning/tuner/batch_size_scaling.py#L161-L162

[mogwai]

Is this coming in to the next release?

[carmocca]

@mogwai This PR still needs to address the comments and write a test etc.

You can work on a new PR to finish it if you are interested in contributing!

[stale]

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