[Refactor] Remove direct import of many methods from `utils`, etc

[kozistr]

Problem (Why?)

N/A

Solution (What/How?)

• [x] Big refactoring, removing direct import from pytorch_optimizer.*.
  • I removed some methods not to directly import from it from pytorch_optimzier.* because they're probably not used frequently and actually not an optimizer rather utils only used for specific optimizers.
  • pytorch_optimizer.[Shampoo stuff] -> pytorch_optimizer.optimizers.shampoo_utils.[Shampoo stuff].
    • shampoo_utils like Graft, BlockPartitioner, PreConditioner, etc. You can check the details here.
  • pytorch_optimizer.GaLoreProjector -> pytorch_optimizer.optimizers.galore.GaLoreProjector.
  • pytorch_optimizer.gradfilter_ema -> pytorch_optimizer.optimizers.grokfast.gradfilter_ema.
  • pytorch_optimizer.gradfilter_ma -> pytorch_optimizer.optimizers.grokfast.gradfilter_ma.
  • pytorch_optimizer.l2_projection -> pytorch_optimizer.optimizers.alig.l2_projection.
  • pytorch_optimizer.flatten_grad -> pytorch_optimizer.optimizers.pcgrad.flatten_grad.
  • pytorch_optimizer.un_flatten_grad -> pytorch_optimizer.optimizers.pcgrad.un_flatten_grad.
  • pytorch_optimizer.reduce_max_except_dim -> pytorch_optimizer.optimizers.sm3.reduce_max_except_dim.
  • pytorch_optimizer.neuron_norm -> pytorch_optimizer.optimizers.nero.neuron_norm.
  • pytorch_optimizer.neuron_mean -> pytorch_optimizer.optimizers.nero.neuron_mean.

Other changes (bug fixes, small refactors)

N/A

Notes

N/A

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (7868588) to head (ceb592a). Report is 25 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #292 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 96 98 +2 Lines 7394 7400 +6 ========================================= + Hits 7394 7400 +6 ```

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