[osipovartem]

Summary

• Use uppercase generated VALUES column names only when unquoted identifier normalization and uppercase mode are enabled.
• Preserve the default lowercase names and the no-normalization mode.
• Rename logical VALUES fields at planning time without adding a runtime projection or per-row work.

Verification

• datafusion-sql sql_integration: 648 passed.
• Independent read-only review: approved, no blocking findings.
• Clippy with -D warnings is blocked by pre-existing warnings in datafusion-common and datafusion-expr under Rust 1.99.