Move private headers out of /include folder

1. The /include folder is exported by export_include_dirs attribute. The
headers for internal use should be moved to another place.
2. Remove unnecessary #inlcude from public headers. So we can have a
compact .lsdump for ABI checker.

Bug: 144407448
Test: atest
Change-Id: I5bb0df02a1ccb70f0e91f4b77668ce54e0127f62
diff --git a/res_stats.cpp b/res_stats.cpp
index 5faf7ca..36dde6b 100644
--- a/res_stats.cpp
+++ b/res_stats.cpp
@@ -21,8 +21,7 @@
 
 #include <android-base/logging.h>
 
-#include "netd_resolv/stats.h"
-
+#include "stats.h"
 
 // Calculate the round-trip-time from start time t0 and end time t1.
 int _res_stats_calculate_rtt(const timespec* t1, const timespec* t0) {