Replace shared_ptr With std::shared_ptr

(This is a merge of http://go/wvgerrit/65783)

Straightforward patch to replace our shared_ptr implementation with
std::shared_ptr, which works identically for all our use cases.

Bug: 111851141
Test: CE CDM Unit Tests
Test: Android Unit Tests
Change-Id: I9e8624dd3cab70a45941a45eb553c1ea0c077d2f

libwvdrmengine/cdm/metrics/include/event_metric.h

@@ -17,7 +17,6 @@
 #include "log.h"
 #include "metrics.pb.h"
 #include "pow2bucket.h"
-#include "shared_ptr.h"
 
 namespace wvcdm {
 namespace metrics {