Deprecate suffixes in merge producing duplicate columns
- [x] closes #22818
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [x] whatsnew entry

I think we should not allow these column collisions at all. Hence deprecating and raising in 2.0
Alternative here would be to add an ``errors`` keyword to the merge and join functions as @simonjayhawkins mentioned in the op. 