Fix test_batch_norm to check module attributes instead of relying on string representation

[drivanov]

The test_batch_norm was recently changed in PR#10647 (Fix CI failing with PyTorch 2.12+), but it still fails with some PyTorh 2.12 versions, and torch-2.12.0a0+0291f960b6.nvinternal.main.46693258 is one of them.

Current PR:

• Replaces brittle str(norm) checks with direct assertions on num_features, eps, momentum, affine, track_running_stats, weight, and bias.
• Removes dependence on WITH_PT212 flag.
• Works correctly with both PyG wrapper BatchNorm and native torch.nn.BatchNorm1d.
• Version-agnostic and future-proof across PyTorch builds.

The fix was tested with :

• torch-2.12.0a0+0291f960b6.nvinternal.main.46693258
• torch 2.10.0a0+a36e1d39eb.nv26.1.42222806

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.18%. Comparing base (c211214) to head (5ba5638).
⚠️ Report is 194 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #10657      +/-   ##
==========================================
- Coverage   86.11%   84.18%   -1.93%     
==========================================
  Files         496      510      +14     
  Lines       33655    36022    +2367     
==========================================
+ Hits        28981    30325    +1344     
- Misses       4674     5697    +1023     

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[puririshi98]

LGTM