Add GREP-377 for Volcano topology-aware scheduling

[xianlubird]

Summary

• Proposes Volcano topology-aware scheduling support for Grove through Volcano HyperNode and PodGroup networkTopology
• Documents how Grove ClusterTopology is materialized as a Volcano HyperNode tree
• Defines PodGang to Volcano PodGroup translation with direct subGroupPolicy usage
• Adds future test expectations for HyperNode sync, drift detection, and topology translation

Key design decisions

• Implement TopologyAwareSchedBackend in the Volcano backend
• Use Volcano HyperNode as the scheduler backend topology resource
• Translate Grove topology constraints to Volcano highestTierAllowed
• Generate a value-level HyperNode tree from Node topology labels
• Keep Grove PodGang as the portable scheduler API and translate to Volcano PodGroup

Fixes #571

[copy-pr-bot]

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