LibCore: Implement System::physical_memory_bytes on Windows

Author: https://github.com/stasoid
Commit: https://github.com/LadybirdBrowser/ladybird/commit/6b86d8a44d7
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3000
Reviewed-by: https://github.com/ADKaster ✅

Libraries/LibCore/SystemWindows.cpp

@@ -239,4 +239,12 @@ unsigned hardware_concurrency()
     return si.dwNumberOfProcessors;
 }
 
+u64 physical_memory_bytes()
+{
+    MEMORYSTATUSEX ms = {};
+    ms.dwLength = sizeof ms;
+    GlobalMemoryStatusEx(&ms);
+    return ms.ullTotalPhys;
+}
+
 }