Add CPU, memory, and accelerator resource requests to PENDING span

[morgan-wowk]

Add resource attributes to PENDING execution spans

execution.resources.cpu, execution.resources.memory, and
execution.resources.accelerators sourced from task_spec annotations.
Enables distinguishing workload types (e.g. Nebius H100 vs GKE L4)
and correlating resource requests to execution timing.

The attributes are attached exclusively to the PENDING status span, where resource reservation is most meaningful. The function try_emit_execution_trace has been renamed to emit_execution_trace to better reflect its role.

Screenshots

[morgan-wowk]

• Add CPU, memory, and accelerator resource requests to PENDING span #258 👈 (View in Graphite)
• Add pipeline/parent context to root execution span #257
• Add cache hit/miss context to root execution span #256
• Add launcher type and cluster URL to root execution span #255
• Add k8s pod/cluster attributes to PENDING status span #254
• Enrich error/success status spans with failure context #253
• Add retroactive OTel execution lifecycle tracing #252
• master

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[morgan-wowk]

Merge activity

• Jun 5, 5:07 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Jun 5, 5:17 PM UTC: Graphite rebased this pull request as part of a merge.
• Jun 5, 5:17 PM UTC: @morgan-wowk merged this pull request with Graphite.