Fixes missing or broken metrics in Widevine CDM

A few metrics were missing or not properly collected in the CDM metrics.
This CL addresses them.

Bug: 64570194
Bug: 72866232

Test: Unit tests and Google Play manual test.
Change-Id: I3a3aa4fb3eb8422c9c8c398016f02409307beb33

libwvdrmengine/cdm/core/include/cdm_engine.h

@@ -18,7 +18,6 @@
 #include "oemcrypto_adapter.h"
 #include "scoped_ptr.h"
 #include "service_certificate.h"
-#include "timer_metric.h"
 #include "wv_cdm_constants.h"
 #include "wv_cdm_types.h"
 
@@ -316,7 +315,6 @@ class CdmEngine {
    * it is published.
    */
   metrics::EngineMetrics metrics_;
-  metrics::TimerMetric life_span_;
 
   CdmSessionMap session_map_;
   CdmReleaseKeySetMap release_key_sets_;