[fix](routineload) Persist the current load definition

[0AyanamiRei]

What problem does this PR solve?

Issue Number: N/A

Related PR: #64878

Problem Summary:

This is Part 1 of the Routine Load target-table ALTER work. It contains only the persistence and recovery prerequisite; it does not add target-table ALTER syntax, fields, or behavior.

RoutineLoadJob currently persists origStmt from CREATE and reparses it during image recovery. Because origStmt never changes, load clauses and job/data-source properties changed by ALTER are not represented by that recovery source.

This PR:

• persists a LoadDefinition snapshot containing the current RoutineLoadDesc, job properties, and data-source properties;
• reconstructs and validates CREATE semantics from LoadDefinition for new images, while retaining origStmt both for reading old images and for older FEs reading new images;
• carries only changed RoutineLoadDesc clauses in ALTER edit logs, then reconstructs the complete definition from runtime state during apply/replay;
• validates failure-prone Kafka and Kinesis ALTER changes before mutating runtime fields, preserving the invariant that LoadDefinition matches the effective runtime CREATE semantics;
• adds image, legacy compatibility, edit-log compatibility, and failed-ALTER atomicity unit tests.

Rollback compatibility: an older FE ignores the unknown LoadDefinition field and follows its existing origStmt recovery path. ALTER semantics applied by the new FE are outside this downgrade guarantee. After rollback, an altered Routine Load job may recover its original load clauses or be cancelled during validation and may need to be recreated.

Release note

Routine Load jobs now recover the current effective load definition after ALTER. If ALTER ROUTINE LOAD is executed after upgrading, rolling back to an earlier FE version may cause the altered job to lose the altered load clauses or be cancelled during image recovery.

Check List (For Author)

• Test
  • Regression test
  • Unit Test
  • Manual test
  • No need to test or manual test
• Behavior changed:
  • No.
  • Yes. New images restore the current effective Routine Load definition; legacy images continue to recover from origStmt.
• Does this need documentation?
  • No.
  • Yes. Document the rollback limitation for jobs altered after upgrade.

[hello-stephen]

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