Standalone Lite: Remaining Utilities

[awaelchli]

What does this PR do?

This PR moves many utilities that are needed for LightningLite in the standalone package.

Reviewer:

Most of the 200+ files are import changes under src/pytorch_lightning. You can skip them in the review and focus on the these items listed here (use the file browser navigation tab):

• src/lightning_lite/utilities: All utilities that are related directly to LightningLite, Acclerator, Strategy, etc. were moved here. Subsequent PRs that move the rest of the code will depend on these utilities being in place.
• src/pytorch_lightning/utilities: Public utilities that were moved receive a deprecation treatment
• tests/tests_lite/helpers: A subset of testing utils have been copied over from PL
• tests/tests_lite/utilities: Tests corresponding to moved functions have been moved here
• tests/tests_pytorch/utilities: All code removed here has moved to the corresponding files in tests/tests_lite/utilities

Notes

• TODO(lite) markers have been added for minor things that need to be resolved in subsequent iterations.
• There are a handful of mypy and flake type errors that we will ignore for now until the rest of the code base gets moved to the right places. TODO(lite) notes have been added.
• There are even more utils that could eventually move to Lite. For now, I'm only picking the ones that are needed to make Lite standalone for the feature set it provides today. Eventually more strategies would move and with it more utils.

cc @Borda @justusschock @awaelchli @rohitgr7 @carmocca @akihironitta