[Fix] explicitly disable weights_only in torch.load to fix tests

[GaetanLepage]

Motivation

Since pytorch v2.6.0, the weights_only parameter of torch.load defaults to True.
This causes some failures in the mmengine test suite:

_pickle.UnpicklingError: Weights only load failed. This file can still be loaded, to do so you have two options, do those steps only if you trust the source of the checkpoint.
    (1) In PyTorch 2.6, we changed the default value of the `weights_only` argument in `torch.load` from `False` to `True`. Re-running `torch.load` with `weights_only` set to `False` will likely succeed, but it can result in arbitrary code execution. Do it only if you got the file from a trusted source.
    (2) Alternatively, to load with `weights_only=True` please check the recommended steps in the following error message.
    WeightsUnpickler error: Unsupported global: GLOBAL mmengine.logging.history_buffer.HistoryBuffer was not an allowed global by default. Please use `torch.serialization.add_safe_globals([HistoryBuffer])` or the `torch.serialization.safe_globals([HistoryBuffer])` context manager to allowlist this global if you trust this class/function.

Check the documentation of torch.load to learn more about types accepted by default with weights_only https://pytorch.org/docs/stable/generated/torch.load.html.

We now need to explicitly disable weights_only when calling torch.load.

Modification

Add weights_only=False to torch.load calls where needed.

BC-breaking (Optional)

No.

Use cases (Optional)

No.

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