[DO NOT MERGE] Revert "Restructed reference root of trust (2/3 DRM Cert)"

This reverts commit f6f5099604.

Reason for revert: Feature missed deadline

Bug: 135283522
Change-Id: Ic86930ee3444c5a6aa1d78ae3a12a9030c29ef92

libwvdrmengine/oemcrypto/ref/src/oemcrypto_engine_ref.cpp

@@ -20,6 +20,7 @@
 #include "keys.h"
 #include "log.h"
 #include "oemcrypto_key_ref.h"
+#include "oemcrypto_rsa_key_shared.h"
 #include "string_conversions.h"
 
 namespace {
@@ -80,10 +81,7 @@ SessionId CryptoEngine::OpenSession() {
 }
 
 SessionContext* CryptoEngine::MakeSession(SessionId sid) {
-  if (root_of_trust_.HasDrmCertKey()) {
-    return new SessionContext(this, sid, root_of_trust_.ShareDrmCertKey());
-  }
-  return new SessionContext(this, sid);
+  return new SessionContext(this, sid, root_of_trust_.SharedRsaKey());
 }
 
 UsageTable* CryptoEngine::MakeUsageTable() { return new UsageTable(this); }