User api updates (#32)

* Update invoke.hpp

* Update OMNITRACE_FUNCTION

* Update library debug messages

* ptl verbosity

* Update timemory submodule

* mpi_gotcha calls omnitrace_finalize_hidden

* omnitrace_{push,pop}_region returns error code

* omnitrace-user updates

- doxygen documentation
- omnitrace_get_user_callbacks
- omnitrace_user_error_string
- omnitrace-user functions return error codes

* Update user-api example

* Tweak to workflows and tests

* Fix for OMNITRACE_FUNCTION

- conditional impl if __GNUC__ < 9

* focal-external-rocm workflow update

[ROCm/rocprofiler-systems commit: f6241af5ee]

projects/rocprofiler-systems/.github/workflows/ubuntu-bionic.yml

@@ -83,7 +83,7 @@ jobs:
       timeout-minutes: 30
       run:
         cd build &&
-        ctest -V --output-log build/omnitrace-ctest-ubuntu-bionic.log
+        ctest -V --output-log build/omnitrace-ctest-ubuntu-bionic.log --stop-on-failure
 
     - name: Test Install
       timeout-minutes: 10