Using hex format allows to better interpret IDs:
the first digits represent the thread number, the last digits represent
the ID within a thread
The main change is in callback.h: PRIu64 -> PRIx64
The patch also guards RUN/CHECK lines in openmp/runtime/tests/ompt with clang-format on/off comments and clang-formats the directory.
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Co-authored-by: Kaloyan Ignatov <kaloyan.ignatov@rwth-aachen.de>