Call LightningDataModule.load_state_dict hook while restoring checkpoint using LightningDataModule.load_from_checkpoint

[rohitgr7]

What does this PR do?

Fixes #14842

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Did you have fun?

Make sure you had fun coding 🙃

cc @awaelchli @ananthsub @ninginthecloud @rohitgr7 @otaj @carmocca @Borda @jjenniferdai @akihironitta

[awaelchli]

@rohitgr7 There are _notebooks changes that were accidentally pushed :)

[tchaton]

LGTM !