Remove runtime.py and directly use torch dist utils + remove unused functions

[kevalmorabia97]

What does this PR do?

• Remove runtime.py and directly use modelopt.torch.utils.distributed functions
• Read model_dtype and autocast_dtype from validate_model_defaults.yaml instead of runtime object
• Remove more unused functions
• Remove unnecessary parse_args for intermediate steps, and improve docstrings

Testing

• No change in functionality
• Existing tests passing

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[danielkorzekwa]

this is used by local distillation: v1/puzzle_tools/bypassed_training/stitched_pipelined.py

[kevalmorabia97]

We can add it when we move local distillation. By that time, we might have also removed sewing kit and instead use Nemo Automdel PP if that works

[codecov]

Codecov Report

❌ Patch coverage is 37.50000% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.47%. Comparing base (74aae83) to head (2f8ef2e).
⚠️ Report is 62 commits behind head on feature/compress.

Files with missing lines	Patch %	Lines
modelopt/torch/utils/distributed.py	37.50%	10 Missing ⚠️

Additional details and impacted files

@@                 Coverage Diff                  @@
##           feature/compress     #667      +/-   ##
====================================================
+ Coverage             74.37%   74.47%   +0.10%     
====================================================
  Files                   182      183       +1     
  Lines                 18219    18416     +197     
====================================================
+ Hits                  13550    13715     +165     
- Misses                 4669     4701      +32     

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