[Libomptarget] Remove debug RAII from libomptarget

This feature was supposed to allow you to trace execution inside of
Libomptarget. However, this never really worked properly. The printing
was always reoganized, only worked for single  threads, and pretty much
only told you a handful of things about a runtime library that's an
implementation detail to all users. Despite this, it contributed about
40% of the total filesize of the deviceRTL. This patch simply removes
this functionalit which I think was past due.

Reviewed By: tianshilei1992

Differential Revision: https://reviews.llvm.org/D157001