chore(includes): migrate to canonical kcenon/thread/* paths (#686)

Update vcpkg consumer integration test to use the canonical
<kcenon/thread/utils/formatter.h> include path. The legacy
<thread_system/utilities/formatter.h> path is now a [[deprecated]]
forwarding header in thread_system and is scheduled for removal
in the next minor release.

Closes #685

Author: kcenon

integration_tests/vcpkg_consumer/main.cpp

@@ -22,7 +22,7 @@
 
 // Tier 1: thread_system (optional)
 #ifdef HAS_THREAD_SYSTEM
-#include <thread_system/utilities/formatter.h>
+#include <kcenon/thread/utils/formatter.h>
 #endif
 
 // Tier 1: container_system (optional)