Libtorch 2.5.1

[dfalbel]

Add support for LibTorch 2.5.1

TODO:

• Update Libtorch M1 builds - and patch the allocator
• Regenerate R level wrappers
• Figure out pre-built binaries for x86_64 macOS
• Drop unsupported CUDA from CI
• Figure out Windows build issues
• Support CUDA 12.4
• Fix crashes related to optional values
• Fix loading of GenericDicts
• Figure out windows deadlocks. Probably related to cleaning up the event loop.
• Figure out failing tests on CUDA:

   -- Failure ('test-distributions-constraints.R:17:3'): positive definite --------
   as_array(object$cpu()) not equal to `expected`.
   10 element mismatches
   Backtrace:
       x
    1. \-torch:::expect_equal_to_r(...) at test-distributions-constraints.R:17:3
    2.   \-testthat::expect_equal(as_array(object$cpu()), expected, ...) at tests/testthat/helper-tensor.R:44:3