Improve buffer flush error handling (#416)

* Update include/rocprofiler-sdk/fwd.h

- add ROCPROFILER_STATUS_ERROR_FINALIZED error code

* Update lib/rocprofiler-sdk/rocprofiler.cpp

- status string for ROCPROFILER_STATUS_ERROR_FINALIZED

* Update lib/rocprofiler-sdk/buffer.cpp

- return error code if buffer flush invoked after finalized
- fatal error if task group destroyed
- error message if task runs after finalized
- improve join of task group

* Update lib/rocprofiler-sdk/counters/tests/evaluate_ast_tests.cpp

- Update lambdas to return reference due to strange -Warray-bounds and -Wstringop-overflow warnings with g++ (Ubuntu 13.1.0-8ubuntu1~20.04.2) 13.1.0

source/include/rocprofiler-sdk/fwd.h

@@ -79,6 +79,7 @@ typedef enum  // NOLINT(performance-enum-size)
     ROCPROFILER_STATUS_ERROR_INVALID_ARGUMENT,  ///< Function invoked with one or more invalid
                                                 ///< arguments
     ROCPROFILER_STATUS_ERROR_METRIC_NOT_VALID_FOR_AGENT,  ///< Invalid metric supplied to agent.
+    ROCPROFILER_STATUS_ERROR_FINALIZED,  ///< invalid because rocprofiler has been finalized
     ROCPROFILER_STATUS_LAST,
 } rocprofiler_status_t;