[FEA] LTO IR Support (4) - Implement LTO Transform Kernels

[lamarrr]

Description

This PR adds LTO-based transforms to libcudf by introducing a new cudf::transform_lto API that accepts LTO-IR or FATBIN UDF binaries and executes them through the existing transform pipeline. The API supports typed transform inputs/outputs, null-awareness, and optional user data.

The change enables libcudf transforms to execute precompiled device UDF fragments instead of relying only on source/PTX-style runtime compilation. This creates a path for lower-overhead, link-time-optimized transform kernels while preserving the existing transform abstraction around input columns, scalar inputs, output specifications, and null policy.

The AOT-compiled transform UDF has a similar ABI signature as NUMBA-CUDA UDFs (https://nvidia.github.io/numba-cuda/user/cuda_ffi.html):

extern "C" __device__ int transform(Output * ... outputs, Inputs... inputs);

The integer return is used for signaling errors (non-zero values) and may be discarded or propagated by the implementation.

This pull request also replaces the software SHA256 implementation with a SIMD-accelerated xxHash implementation (XXH3-128, ported from #22920). SHA256 was initially chosen as the obvious choice for a collision-free hash, and it was implemented to keep dependencies minimal.

For a hot JIT cache, the previous cryptographic SHA256 hash took ~88.1% (~4727ns) of the get_kernel function execution time.
With the new non-cryptographic SIMD-accelerated hash, the hash time is reduced by 16.33x to 288ns, ~31.2% of the get_kernel function execution time.

This pull request also:

• Hoists the cudaGetDeviceProperties values into the cudf context object; each call takes ~1.8ms per-call (see: [BUG] Repeated calls to cudaGetDeviceProperties causes launch overhead in JIT kernels #23074)
• Refactors librtcx's CMake functions to comply with RAPIDS' naming standards
• Makes the nvrtc-related flags be dispatched by the nvrtcVersion and not cudaGetRuntimeVersion. They can be different
• Removes discard_errors specialization of the transform kernel; this helps reduce the number of kernel instantiations that need to be pre-compiled, and also reduces kernel variance

Closes #19578 & #23074

Benchmarks

Throughput benchmarks are provided in #22680 (comment), and compilation-time benchmarks are provided in #22680 (comment)

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[lamarrr]

/ok to test 9cfd77f

[lamarrr]

/ok to test 19e47b9

[lamarrr]

/ok to test 543e226

[lamarrr]

/ok to test f730f36

[lamarrr]

/ok to test a2034e2

[lamarrr]

/ok to test 5a85802

[lamarrr]

/ok to test f7d2883

[lamarrr]

/merge