BUG: Raise MergeError when suffixes result in duplicate column names …
closes #61402 

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 Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
 Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

pre-commit.ci autofix Thanks for your contribution!

Just a quick note: you don't need to write `GH#61402` in the PR description — simply using `#61402` in PR description, is enough, GitHub will automatically link it 😀. 
Also, since this PR addresses a bug, please make sure to:
* Add a unit test that covers this case
* Include an entry in the `doc/source/whatsnew/vx.y.z.rst` file to document your fix

For reference, you can check the contributing guidelines here: https://pandas.pydata.org/docs/development/contributing_codebase.html#documenting-your-code Thanks for the pointers.  I'll get those added in here soon.  Trying to track down why the Unit Tests / Linux-32-bit(pull_request) is failing.  I didn't change anything that should have effected Series, so it's kinda weird.  

I also can't get the pytest to run normally on my dev yet either, so I haven't been able to fully replicate the failure locally yet.  So, still a little more work to do here. @Farsidetfs I believe the CI failure is not related to your changes. It appears to be caused by the cython version — pandas unit tests fail with `cython==3.1.0`. You may notice that the same test failures have occurred in several recent PRs as well. I already address the issue in https://github.com/pandas-dev/pandas/pull/61423.  pre-commit.ci autofix pre-commit.ci autofix pre-commit.ci autofix pre-commit.ci autofix @nikaltipar I think this should be ready now.  Please let me know if I've missed anything.  I took your advice and combined the two with slight modifications to improve efficiency using sets throughout rather than just convert at the end. > @nikaltipar I think this should be ready now. Please let me know if I've missed anything. I took your advice and combined the two with slight modifications to improve efficiency using sets throughout rather than just convert at the end.

Thanks for taking care of that, @Farsidetfs ! It looks good to me, no other comments from my side. Thanks for adding the unit-tests, too! @nikaltipar Could you rebase main branch to trigger CI again? > @nikaltipar Could you rebase main branch to trigger CI again?

I am not able to, I'll have to wait for @Farsidetfs  Rebase complete.  Thanks.  Let me know if there's anything else needed. #61402  @rhshadrach All requested changes are complete, so it should be ready for your review to unblock merge.  Thanks @Farsidetfs - just a conflict that needs resolved in the whatsnew. pre-commit.ci autofix pre-commit.ci autofix @rhshadrach Merge conflicts resolved, ready for merge Thanks @Farsidetfs very nice