runtime: add new functions total_memory/0 and free_memory/0 (#18499)

vlib/runtime/runtime_windows.c.v

@@ -7,7 +7,14 @@ struct C.SYSTEM_INFO {
 	dwNumberOfProcessors u32
 }
 
+[typedef]
+struct C.MEMORYSTATUS {
+	dwTotalPhys usize
+	dwAvailPhys usize
+}
+
 fn C.GetSystemInfo(&C.SYSTEM_INFO)
+fn C.GlobalMemoryStatus(&C.MEMORYSTATUS)
 
 // nr_cpus returns the number of virtual CPU cores found on the system.
 pub fn nr_cpus() int {
@@ -19,3 +26,17 @@ pub fn nr_cpus() int {
 	}
 	return nr
 }
+
+// total_memory returns total physical memory found on the system.
+pub fn total_memory() usize {
+	memory_status := C.MEMORYSTATUS{}
+	C.GlobalMemoryStatus(&memory_status)
+	return memory_status.dwTotalPhys
+}
+
+// free_memory returns free physical memory found on the system.
+pub fn free_memory() usize {
+	memory_status := C.MEMORYSTATUS{}
+	C.GlobalMemoryStatus(&memory_status)
+	return memory_status.dwAvailPhys
+}