cherry-pick: shared source bug fixes (#19578, #19564) to 2.1

[xxchan]

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What's changed and what's your intention?

• fix(planner): correctly handle hidden columns for SourceBackfill #19578
• fix(meta): locate upstream source fragment correctly for SourceBackfill #19564

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have added test labels as necessary. See details.
• I have added fuzzing tests or opened an issue to track them. (Optional, recommended for new SQL features Sqlsmith: Sql feature generation #7934).
• My PR contains breaking changes. (If it deprecates some features, please create a tracking issue to remove them in the future).
• All checks passed in ./risedev check (or alias, ./risedev c)
• My PR changes performance-critical code. (Please run macro/micro-benchmarks and show the results.)

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If this PR includes changes that directly affect users or other significant modifications relevant to the community, kindly draft a release note to provide a concise summary of these changes. Please prioritize highlighting the impact these changes will have on users.

[graphite-app]

Graphite Automations

"release branch request review" took an action on this PR • (11/26/24)

1 reviewer was added to this PR based on xxchan's automation.

[xxchan]

The error in the tests seems fine

thread '<unnamed>' panicked at /risingwave/src/tests/sqlsmith/src/test_runners/fuzzing.rs:37:57:
called `Result::unwrap()` on an `Err` value: Encountered unexpected error: db error: ERROR: Failed to run the query

Caused by:
  Expr error: error while evaluating expression `sqrt_f64('-7768382570.666667')`: Invalid parameter sqrt input: input cannot be negative value

[xxchan]

reapplied changes. need another approve