[C++] Improve error handling for hash table merges

[asfimport]

A simple function has been added for merging elements of a hash table into another. At the moment, a warning is logged if this fails; presumably, the elements have already been added to a hash table so the risk should be low.

 

At some point, we should improve this error handling:

    #13583 (comment)

Reporter: Aldrin Montana / @drin

_{Note: This issue was originally created as ARROW-17074. Please see the migration documentation for further details.}

[helloitsheqing]

Hi team! I was wondering if anyone is currently working on this issue and if not, if I am able to take a shot at it?
Thank you.

[kou]

Nobody is working on this. Could you try this?

[helloitsheqing]

Will do and keep you updated, thank you!

[kris-gaudel]

Take

[zanmato1984]

Issue resolved by pull request 49512
#49512