feat(meta): align splits with source actor with an upstream

[xxchan]

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[xxchan]

Current dependencies on/for this PR:

• main
  • PR refactor(frontend): improve readability of LogicalSource #14687
    • PR refactor: minor refactor on fragment graph building #14560
      • PR refactor(stream): SourceExecutor minor refactor #14706
        • PR feat(stream): add kafka backfill executor #14172
          • PR feat: add kafka backfill frontend #14465
      • PR feat(meta): align splits with source actor with an upstream #14171 👈

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