Add PyTorch 2.5.0 to CI

[BenjaminBossan]

• Drop 2.1.2, update 2.4.0 to 2.4.1
• Drop Python 3.8, add Python 3.12
• Filter new torch warning about weights_only as that trips up some warning tests
• Unpin protobuf from dev requirements
• Filter warnings caused by usage of utcnow by protobuf
• Skip torch.compile tests when torch < 2.4 and Python 3.12 are used, as this is not supported by torch

Note that I had to upgrade torch and Python at the same time because torch 2.5 requires Python > 3.8 and because Python 3.12 requires torch > 2.1 (which is dropped in favor of 2.5).

[BenjaminBossan]

~CI needs #1070 first, as torch 2.5 is not available for Python 3.8.~