Add system-provided CUDA library targets

[cjm-dd]

Summary

Adds a system-provided sibling for each CUDA shared-library target. Consumers can select foo_system when CUDA is supplied by the runtime environment, while the existing foo and foo_static targets keep their current behavior.

At the lowest layer, each existing cc_import named *_shared_library now has a matching *_interface_library import with system_provided = True. The public foo_system wrappers mirror the dependency relationships of foo, while the interface imports themselves remain independent of other interface imports. This keeps the imports lightweight and makes composition explicit at the public target layer.

Header dependency closure now lives on each component's headers target. As a result, shared, static, and system-provided variants all receive the headers they need, but the system-provided graph does not acquire any packaged *_shared_library targets.

The interface imports prefer NVIDIA's lightweight linker stubs under lib/stubs/ whenever the redistribution ships them. Archives without a stub use the unversioned DSO as the interface-only linker input. The relevant component archives were checked across every supported CUDA version and applicable Linux x86_64/SBSA variant; the notable compatibility exception is CUDA 12.1.1's nvJitLink archive, which does not contain a stub and therefore falls back to lib/libnvJitLink.so.

The README documents the new target convention and the requirement that foo_system consumers provide the corresponding runtime libraries.

Validation

• buildifier -mode=check on the changed BUILD and Starlark files
• git diff --check
• downstream Bzlmod consumer builds that compile component headers in isolation and link an aggregate system-interface target for CUDA 12.1.1, 12.8.1, and 13.2.1
• configured dependency query confirming that the aggregate system-provided graph contains no *_shared_library labels
• archive-member inventory across all 29 supported CUDA versions (594 version/platform records, 460 unique archives)

[cerisier]

That's just great thanks :)