[FEA]: Add a large-block segmented-sort kernel using the runtime-width group merge primitive #10949

Is this a duplicate?

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Area

CUB

Is your feature request related to a problem? Please describe.

Fine-grained segmented-sort planning can assign 512 or 1024 cooperating threads to a segment that fits within a CTA-scale tile. A kernel is needed to consume these large-block work-plan configurations.

Describe the solution you'd like

Add a large-block segmented-sort kernel that:

• Consumes work-plan configurations using 512 or 1024 threads per segment.
• Uses the runtime-width group merge-sort primitive tracked in [FEA]: Add a runtime-width group merge-sort primitive for segmented sort #10944.
• Supports the shared-memory requirements and partially filled tiles for these configurations.
• Provides correctness coverage for the supported widths and sort modes.

Segments exceeding the supported CTA-scale capacity remain the responsibility of the fallback or separate large-segment load-balancing work.

This issue can be closed once the kernel is implemented in cub::detail and tested as a consumer of the large-block work-plan tier.

Describe alternatives you've considered

Separate sorting implementations for each width are unnecessary because they share the runtime-width primitive.

Additional context

Parent tracking issue: #10946.