[OpenMP] Consolidate error handling and debug messages in Libomptarget

Summary:

This patch consolidates the error handling and messaging routines to a single
file omptargetmessage. The goal is to simplify the error handling interface
prior to adding more error handling support

Reviewers: jdoerfert grokos ABataev AndreyChurbanov ronlieb JonChesterfield ye-luo tianshilei1992

Subscribers: danielkiss guansong jvesely kerbowa nhaehnle openmp-commits sstefan1 yaxunl