[libomptarget] Always call malloc, free via SafeMalloc, SafeFree wrapper

Summary:
[libomptarget] Always call malloc, free via SafeMalloc, SafeFree wrapper

NFC for release, adds some verbosity to debug printing. Motivation is to provide
one place where local modifications can be made to the behaviour of all heap
allocation or deallocation while debugging.

Reviewers: jdoerfert, ABataev, grokos

Reviewed By: ABataev

Subscribers: openmp-commits

Tags: #openmp

Differential Revision: https://reviews.llvm.org/D69492