[fix](fe) Propagate JSON properties for multi-table routine load

[0AyanamiRei]

What problem does this PR solve?

Issue Number: None

Related PR: None

Problem Summary: Multi-table routine load cannot attach a table-specific pipeline plan before the backend discovers the destination table. The backend therefore requests a per-table plan with the format, and FE rebuilds the stream-load task from the Routine Load job. That rebuild already restored json_root and strip_outer_array, but omitted jsonpaths and num_as_string. Nested JSON records were consequently planned with an empty JSON path list and filtered as invalid rows. This change restores those two properties before generating each dynamic-table pipeline plan.

Release note

Fix multi-table routine load to honor jsonpaths and num_as_string for dynamic target tables.

Check List (For Author)

• Test

  • Regression test
  • Unit Test
    • sh run-fe-ut.sh --run org.apache.doris.nereids.load.NereidsStreamLoadTaskTest
    • DISABLE_BUILD_UI=ON ./build.sh --fe -j48
  • Manual test
  • No need to test or manual test.

• Behavior changed:

  • No.
  • Yes. Multi-table routine load now applies configured jsonpaths and num_as_string during per-table planning.

• Does this need documentation?

  • No.
  • Yes.

Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
• Confirm document
• Add branch pick label

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