refactor!: move ordering-related code to `order_by_util.rs` && fix an issue with decimals

[iajoiner]

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Rationale for this change

OrderByExec (to be added), GroupByExec and SortMergeJoinExec (to be added) all depend on correct sorting of rows. Hence we move them together. Meanwhile a bug was found in compare_indexes_by_owned_columns_with_direction causing negative decimals to be considered larger than positive ones. Hence we fixed it and modified a test to check for that.

What changes are included in this PR?

• move ordering-related manipulations from group_by_util.rs and owned_column.rs to order_by_util.rs
• fix the bug mentioned above.

  Yes.

[github-actions[bot]]

:tada: This PR is included in version 0.50.0 :tada:

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