[OpenMP] Add using bit flags to select Libomptarget Information

Summary:
This patch adds more fine-grained support over which information is output from the libomptarget runtime when run with the environment variable LIBOMPTARGET_INFO set. An extensible set of flags can be used to pick and choose which information the user is interested in.

Reviewers: jdoerfert JonChesterfield grokos

Differential Revision: https://reviews.llvm.org/D93727