[Bugfix] Fix Crashing When Loading Modules With Batchnorm Stats

[alex-jw-brooks]

Currently, the AutoWeightsLoader crashes if it encounters batch normalization stats in the model's safetensors. This is because the bn stats aren't part of the named_parameters, but they are part of the state dict, likely due to the reasons mentioned on the PyTorch forums here.

This PR adds loading the bn stats for the the torch module _BatchNorm's subclasses, as well as some tests that currently throw ValueErrors.

(This fix is needed for the upcoming granite speech models from our group. Currently, there aren't many models in vLLM that use batchnorm except for phi4mm audio, which disables it by default, which is why it probably hasn't popped up before).

CC @njhill @tlrmchlsmth

[github-actions]

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[DarkLight1337]

Nice catch, thanks for fixing!