fix(Util): shutdown logging channels to prevent AsyncChannel deadlock on exit

[matejk]

Summary

• Fixes deadlock when app exit if AsyncChannel is used in the logging system #5228 - deadlock when app exits if AsyncChannel is used in the logging system
• LoggingSubsystem::uninitialize() was empty, so AsyncChannel's background thread was still running when static destruction began, causing deadlock on destroyed mutexes
• Added Logger::shutdown() and LoggingRegistry::defaultRegistry().clear() calls to uninitialize() to ensure all channels are properly closed before static destruction
• Added unit test testAsyncChannelShutdown to verify the fix

Test plan

• Added LoggingConfiguratorTest::testAsyncChannelShutdown unit test
• All 227 Util tests pass
• Verify with the reproduction steps from deadlock when app exit if AsyncChannel is used in the logging system #5228 (SampleApp with AsyncChannel properties config)