Added ERROR message class to handle fatal error messages. (#2002)

* Added ERROR message class to handle fatal error messages.

New ERROR message class will print the message in all debug level,
including none.

Change some of the fatal error message to be in ERROR instead of WARN.

Added new error handler function to print out more meaningful error
message in the future.

* Added CHANGELOG entry.

* Update CHANGELOG.md

Co-authored-by: Jeffrey Novotny <jnovotny@amd.com>

* Change to no longer reuse NONE as ERROR. ERROR is now a separated class.

* Update CHANGELOG.md

Co-authored-by: Jeffrey Novotny <jnovotny@amd.com>

---------

Co-authored-by: Jeffrey Novotny <jnovotny@amd.com>

ext-tuner/example/test/test_plugin.c

@@ -62,7 +62,8 @@ void mock_logger(ncclDebugLogLevel level, unsigned long flags,
   // Convert log level to string
   const char* level_str;
   switch(level) {
-    case NCCL_LOG_NONE: level_str = "NONE"; break;
+    case NCCL_LOG_NONE: level_str = "NONE"; break;	  
+    case NCCL_LOG_ERROR: level_str = "ERROR"; break;
     case NCCL_LOG_VERSION: level_str = "VERSION"; break;
     case NCCL_LOG_WARN: level_str = "WARN"; break;
     case NCCL_LOG_INFO: level_str = "INFO"; break;