Changes to clean_names de-duplication broke existing CRAN packages

[sfirke]

Re: #495 (comment)

I ran revdep_check() and found that at least BFS and nflfastR packages are broken by the change to how duplicate names get _1, _2 etc. suffixes. That makes me inclined not to include the changes from #495 as-is for this CRAN release. I see at least these options:

1. Rework the code to let users allow_dupes while keeping the existing patterns of resulting names. Submit this month to CRAN, won't break other packages.
2. Option 1, except after 2.2 release this month so this doesn't have to be a rush job
3. Keep the breaking change, but delay it. Pull this PR out of the January 2023 release of 2.2, add it back to the dev branch, notify maintainers of affected packages and help them if needed.

[sfirke]

Silly Github! You ate my issue, gave me a 404 error, and now I have two copies? Boo.

[sfirke]

Duplicate of #513