feat!: Avoid appending a numeric suffix to duplicate column names

[krlmlr]

Closes #321.

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This pull request failed to merge: PR cannot be automatically rebased, please rebase manually to continue. Once the issues are resolved, remove the blocked label and re-queue the pull request. Note that the pull request will be automatically re-queued if it has the mergequeue label.

Additional debug info: Failed to rebase this PR onto the latest changes from the base branch. You will probably need to rebase this PR manually and resolve conflicts).

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This pull request failed to merge: some CI status(es) failed. Once the issues are resolved, remove the blocked label and re-queue the pull request. Note that the pull request will be automatically re-queued if it has the mergequeue label.

Failed CI(s): Smoke test: stock R