Kernel: Migrate hostname locking to ProtectedValue

Author: https://github.com/boricj
Commit: 626b99ce1c
Pull-request: https://github.com/SerenityOS/serenity/pull/8851
Reviewed-by: https://github.com/awesomekling ✅
Reviewed-by: https://github.com/bgianfo

Kernel/Process.h

@@ -22,6 +22,7 @@
 #include <Kernel/Forward.h>
 #include <Kernel/FutexQueue.h>
 #include <Kernel/Locking/Mutex.h>
+#include <Kernel/Locking/ProtectedValue.h>
 #include <Kernel/Memory/AddressSpace.h>
 #include <Kernel/PerformanceEventBuffer.h>
 #include <Kernel/ProcessGroup.h>
@@ -33,6 +34,7 @@
 
 namespace Kernel {
 
+ProtectedValue<String>& hostname();
 Time kgettimeofday();
 
 #define ENUMERATE_PLEDGE_PROMISES         \