Build metrics_dump tool in Android.

Replace Makefile with Android.bp.
Remove duplication of protos in proto directory.

Since we are now building the metrics_dump tool
under Android, use frameworks metrics.proto
directly. Also, reference cdm's wv_metrics.proto
from the cdm directory instead of creating a
subset in proto directory.

bug: 161783052
bug: 170607430

Test: build
  m -j128 metrics_dump
Test: metrics_dump [bugreport from adt-3-r.zip]
Test: metrics_dump [bugreport from sabrina-q.gz]
Test: metrics_dump --widevine [adb shell dumpsys media.metrics output]
Change-Id: I82c7e723453ac2a6335cb2bb732a376d535b9ea3

libwvdrmengine/tools/metrics_dump/src/mediadrm_metrics.cpp

@@ -11,7 +11,7 @@
 #include <sstream>
 #include <string>
 
-#include "mediadrm_metrics.pb.h"
+#include "metrics.pb.h"
 
 namespace mediadrm_metrics {