Minitron pruning refactor [2/2]: De-couple importance estimator from Dynamic Module

[kevalmorabia97]

What does this PR do?

• Code refactor, no logic change
• De-couple Minitron pruning importance estimator from Dynamic Module so its easy to configure different importance logic for pruning

Testing

• CI/CD tests passing
• Compare mmlu on pruned Qwen3-8B with previous and current implementation
• Compare mmlu on pruned Qwen3-30B-A3B with previous and current implementation (lot of variance in results, some pruning configs better some worse)
• Compare mmlu on pruned Nemotron-Nano-v2-9B with previous and current implementation

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.72%. Comparing base (10d0fec) to head (e1c884e).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #693   +/-   ##
=======================================
  Coverage   74.72%   74.72%           
=======================================
  Files         192      192           
  Lines       18828    18828           
=======================================
  Hits        14070    14070           
  Misses       4758     4758           

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