Move _worker_check() logic to process_dataloader() in DDPSpawnStrategy class.

[ninginthecloud]

Proposed refactor

This issue follows @ananthsub 's #11756 to move strategy-specific dataloader logic to the stategies.

Motivation

_worker_check() in data_connector.py is used to check the number of workers for the dataloader when user sets up DDP_SPAWN strategy.
https://github.com/PyTorchLightning/pytorch-lightning/blob/cc43d07db1ab77385feff04c01f040c5cad805a9/pytorch_lightning/trainer/connectors/data_connector.py#L274

Since this dataloader verfication logic is dpp_spawn strategy specific, it'll be better we moved the logic to DDPSpawnStrategy class. By doing so, _worker_check() can be removed from data_connector.py.

Pitch

This logic check could be moved to process_dataloader() in DDPSpawnStrategy class.

Additional context

cc: @edward-io @four4fish @ananthsub

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cc @justusschock @awaelchli @ninginthecloud @rohitgr7 @otaj @tchaton @akihironitta

[awaelchli]

Closing because no longer relevant. The logic was recently reworked (#18737, #18649, #18591) and the worker_check function is no longer just ddp-spawn specific.