[llvm] [mlir] [OMPIRBuilder][OpenMP][LLVM] Modify and use ReplaceConstant utility in convertTarget (PR #94541)

[via llvm-commits]

agozillon wrote:

Updated the comment in the last commit to provide details on the arguments! Thank you very much @jsjodin and @nikic I will merge the changes now. 

https://github.com/llvm/llvm-project/pull/94541