GlobalLogHandler usage may lead to UB

OpenTelemetry-cpp library provides the only one way to log own errors: to use singletone that located under the hood of class GlobalLogHandler.
GlobalLogHandler::GetHandlerAndLevel() may provide a reference to destroyed object if called during app finalization. It will lead to undefined behaviour. "if (!log_handler)" in OTEL_INTERNAL_LOG_DISPATCH macro will not cover this case. I will provide a code snipped if you need it.

Also, there's one more problem with stateful singletone.
I have an integration test in my project that runs several modules in a single process. I can't guarantee that correct global handler will be set if such setup is a part of initialization of every module.

So, I would propose to avoid mandatory singletone usage. I think that correct way is to initialize classes with LogHandlerProvider.

Start by reviewing GlobalLogHandler::GetHandlerAndLevel() and the OTEL_INTERNAL_LOG_DISPATCH macro, then investigate the reported finalization and multi-module initialization cases. Done means the logging path no longer permits a reference to a destroyed object and the handler behavior is defined for modules initialized in one process.