Add NCCL redist support

[cerisier]

Summary

• add optional NCCL redist support via nccl_version / nccl_patches on cuda_ext.redist(...)
• add NCCL wheel metadata for CUDA 12 and CUDA 13 on linux x86_64 and SBSA
• include all CUDA 12/13 NCCL wheel versions currently carried by rules_ml_toolchain: 2.27.7, 2.28.9, 2.29.2, 2.29.3, 2.29.7, 2.30.4
• expose @cuda//nccl proxy targets and add an e2e nccl_smoke target

Validation

• jq empty nccl/nccl_redist_versions.json
• bazel build //...
• cd e2e && bazel build //:cudnn_smoke //:nccl_smoke --platforms //:platform_linux_amd64_cuda_13_3_0
• temporarily selected NCCL 2.27.7, then validated cd e2e && bazel build //:nccl_smoke --platforms //:platform_linux_amd64_cuda_12_9_1
• temporarily selected NCCL 2.27.7, then validated cd e2e && bazel build //:nccl_smoke --platforms //:platform_linux_amd64_cuda_13_3_0

Notes

• NCCL smoke is tagged manual because the wheel is large.
• Keeps existing platform semantics; no linux-sbsa/linux-aarch64 split.