Entitlement rotation support

Updates also include:
- Add APIs to query current Simulcrypt channel & stream status;
- EMM format change (used only to carry fingerprinting and service
blocking info);
- Key fetcher example to use curl key fetcher.

common/rsa_key.h

@@ -18,9 +18,7 @@
 #include <memory>
 #include <string>
 
-#include <cstdint>
-#include "absl/base/macros.h"
-#include "openssl/rsa.h"
+#include "openssl/pem.h"
 #include "common/hash_algorithm.h"
 
 namespace widevine {