Alter paren padding for no-decimal cols

[steveputman]

Summary

This PR adds some flow control to cols_align_decimal() for cases where the affected column is devoid of decimal marks. In those situations, the decimal mark imputed in the function should be replaced by an empty string rather than a space, and the non-breaking space should pad the numbers without parens instead of the numbers with parens.

Related GitHub Issues and PRs

• Refs:
• Decimal alignment with cols_align_decimal() #1058
• Request for additional functionality for cols_align_decimal #1076

Checklist

• I understand and agree to the Code of Conduct.
• I have listed any major changes in the NEWS.
• I have added testthat unit tests to tests/testthat for any new functionality.

[rich-iannone]

Thanks and lgtm!