Add scontrol_topology GCM monitor for periodic Slurm topology collection

[mitthu]

Summary:
Adds a new GCM monitor that runs scontrol show topo every 60 seconds and publishes the results as logs for the fair_slurm_topology Scuba table. This supports two use cases from T275974051: SLA compliance monitoring for partial racks and topology-aware job debugging for GB300.

The monitor handles both block topology format (BlockName/BlockIndex/BlockSize, used on CW clusters) and switch/tree topology format (SwitchName/Level/LinkSpeed/Switches). Node lists in Slurm hostlist notation (e.g., g3-129-[057,059,063]) are expanded into individual node names using the existing nodelist() parser, with a 10000-entry truncation safety limit.

Differential Revision: D110108419

[meta-codesync]

@mitthu has exported this pull request. If you are a Meta employee, you can view the originating Diff in D110108419.

[github-actions]

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