Integrate lightning_utilities get_all_subclasses

[carmocca]

What does this PR do?

Part of #14492
Part of Lightning-AI/utilities#39

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

None

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cc @Borda @justusschock @awaelchli @rohitgr7 @akihironitta

[tchaton]

LGTM !