[Bugfix] Fix sleep mode level 2

[Potabk]

What this PR does / why we need it?

For sleep mode level 2, we discarded model both weights and kv_cache, but the problems is: When we discard weights, we also discard some tensors representing the model state which we called model.named_buffers(), such as: running_mean / running_var in BatchNorm、rope cos-sin cache ... when we update weights, but forgot to update buffers as well, this will lead to some unknown issue

Does this PR introduce any user-facing change?

How was this patch tested?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 27.36%. Comparing base (c30ddb8) to head (1b422c0).
Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1376      +/-   ##
==========================================
- Coverage   27.39%   27.36%   -0.04%     
==========================================
  Files          56       56              
  Lines        6191     6184       -7     
==========================================
- Hits         1696     1692       -4     
+ Misses       4495     4492       -3     

Flag	Coverage Δ
unittests	27.36% <ø> (-0.04%)	⬇️

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