[OpenMP] [OMPT] [amdgpu] [4/8] Implemented callback registration in amdgpu plugin

[dhruvachak]

Summary

The purpose of this patch is to Implement registration of callback functions in the amdgpu plugin by looking up corresponding callbacks in libomptarget. The overall design document is https://rice.app.box.com/s/pf3gix2hs4d4o1aatwir1set05xmjljc

Defined an object of type OmptDeviceCallbacksTy in the amdgpu plugin for holding the tool-provided callback functions. Implemented a global constructor in the plugin that creates a connector object to connect with libomptarget. The callbacks that are already registered with libomptarget are looked up and registered with the plugin.

Depends on D123974

Patch from John Mellor-Crummey <[e-mail]>
(With contributions from Dhruva Chakrabarti <[e-mail]>)

[dhruvachak]

Rebased

[jplehr]

openmp/libomptarget/plugins/amdgpu/src/ompt_callback.cpp

57

Minor change to be consistent with other functions printing the function name in these debug messages.