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

source/bin/CMakeLists.txt

@@ -2,6 +2,6 @@ add_subdirectory(omnitrace-avail)
 add_subdirectory(omnitrace-critical-trace)
 add_subdirectory(omnitrace)
 
-if(OMNITRACE_BUILD_TESTING)
+if(OMNITRACE_BUILD_TESTING OR "$ENV{OMNITRACE_CI}" MATCHES "[1-9]+|ON|on|y|yes")
     add_subdirectory(tests)
 endif()