[OpenMP] Use function tracing RAII for runtime functions.

This patch adds support for using function tracing features to track the
executino of runtime functions in the device runtime library. This is
enabled by first compiling the new runtime with
`-fopenmp-target-debug=3` and running with
`LIBOMPTARGET_DEVICE_RTL_DEBUG=3`. The output only tracks team 0 and
thread 0 so there isn't much output when using a generic region.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D112002