chore: use into_parts for owned record batches columns in mito2

[lyang24]

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What's changed and what's your intention?

avoids one extra Vec allocation

PR Checklist

Please convert it to a draft if some of the following conditions are not met.

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.
• API changes are backward compatible.
• Schema or data changes are backward compatible.

[gemini-code-assist]

Code Review

This pull request refactors the handling of RecordBatch objects across several files, including compat.rs, parquet.rs, and flat_format.rs. The changes replace the pattern of cloning columns and accessing schemas separately with the into_parts() method, which decomposes the batch into its constituent components. This refactoring likely improves efficiency by avoiding unnecessary clones. I have no feedback to provide as there were no review comments to evaluate.