Add Missing Includes Netflix Pointed Out

(This is a merge of http://go/wvgerrit/66810)

Netflix discovered that several files were only compiling because of
transitive includes via the Metrics code. This patch adds the missing
headers they noted.

Bug: 118676365
Test: CE CDM Build
Change-Id: Ifbc4e5d4276d1c3fb9bbd677230cd431e34e5c76

libwvdrmengine/cdm/core/include/key_session.h

@@ -5,7 +5,11 @@
 #ifndef WVCDM_CORE_KEY_SESSION_H_
 #define WVCDM_CORE_KEY_SESSION_H_
 
+#include <vector>
+
 #include "metrics_collections.h"
+#include "OEMCryptoCENC.h"
+#include "wv_cdm_types.h"
 
 namespace wvcdm {