Release eval: job to measure data-lake backfill ingestion perf

[Shaptic]

Parent: #706
Depends on: #707

Summary

Add a release-evaluation job that measures RPC database load while backfilling from public pubnet ledger data without relying on live Core nodes.

Scope

• Start stellar-rpc with --backfill, --serve-ledgers-from-datastore, pubnet network settings, and a public data-lake datastore configuration.
• Use an isolated SQLite DB path on the runner and collect DB size, runtime, ledgers/sec, and final health/latest-ledger state.
• Backfill with a hardcoded history-retention-window.
• Validate that no Stellar Core node is required for the backfill ingestion path.

Acceptance criteria

• The job can ingest a configured pubnet ledger window from public data-lake files and exit deterministically.
• The job fails when metrics exceed TBD thresholds.
• Metrics and logs are uploaded for final reporting.