fix: handle empty IEJoin outer fill

[sundy-li]

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Summary

• avoid IEJoin outer-fill panics when the unmatched inner side produced no data blocks
• build null-padded outer rows from the range-join output schema instead of indexing an empty inner block vector
• add a direct unit regression plus SQL/integration coverage for empty-input outer IEJoin cases

Changes

1. Store the range-join output schema in RangeJoinState.
2. Update fill_outer() to derive the null-padded inner columns from the output schema slices for left/right joins.
3. Add a unit test that reproduces the reported out-of-bounds panic with an empty inner block vector.
4. Add SQL execution coverage and a sqllogictest file for outer IEJoin queries with empty inputs.

Tests

• cargo test -p databend-query test_fill_outer_with_empty_inner_table_blocks --lib -- --nocapture
• cargo test -p databend-query --test it test_iejoin_outer_join_with_empty_input -- --nocapture
• cargo clippy -p databend-query --lib -- -D warnings

Type of change

• Bug fix

Fixes #19569

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[github-actions]

At least one test kind must be checked in the PR description.
@sundy-li please update it 🙏.