Move Stopwatch to libnetdutils

Move Stopwatch to libnetdutils as it is an useful utility across
netd and the resolver library.

Bug: 128662167
Test: system/netd/tests/runtests.sh passed

Change-Id: Iebaffc66202fbe3a787ca645847762af1ed94bd7
diff --git a/client/NetdClient.cpp b/client/NetdClient.cpp
index 195c45d..bc8d3fc 100644
--- a/client/NetdClient.cpp
+++ b/client/NetdClient.cpp
@@ -32,12 +32,13 @@
 #include "Fwmark.h"
 #include "FwmarkClient.h"
 #include "FwmarkCommand.h"
-#include "Stopwatch.h"
+#include "netdutils/Stopwatch.h"
 #include "netid_client.h"
 
 #include "android-base/unique_fd.h"
 
 using android::base::unique_fd;
+using android::netdutils::Stopwatch;
 
 namespace {