[LIBOMPTARGET]Fix PR44933: fix crash because of the too early deinitialization of libomptarget.

Summary:
Instead of using global variables with unpredicted time of
deinitialization, use dynamically allocated variables with functions
explicitly marked as global constructor/destructor and priority. This
allows to prevent the crash because of the incorrect order of dynamic
libraries deinitialization.

Reviewers: grokos, hfinkel

Subscribers: caomhin, kkwli0, openmp-commits

Tags: #openmp

Differential Revision: https://reviews.llvm.org/D74837