Checkpointer load should specify weights_only

[baldassarreFe]

From pytorch 2.6 (next release), ``torch.loadwill switch the default forweights_only` from `False` to `True`. I was training models using 2.5 (which defaults to `weights_only=True`) and when I switched to 2.6 I got an exception when resuming a checkpoint because fvcore doesn't pass that parameter and the the default is now `False`:

fvcore/fvcore/common/checkpoint.py

Line 254 in a491d5b

return torch.load(cast(IO[bytes], file), map_location=torch.device("cpu"))

I think Checkpointer should allow passing a value for weights_only, either in the constructor or in Checkpointer.load().
It's a trivial modification to the code, but it's worth discussing where to introduce the new parameter before proposing a PR.