Cleanup drm_hal_clearkey_test.

To stay close to the original test, the only time the test will abort is
when it encounters errors in Setup.

The following changes are applied in this CL:

- #include <openssl/aes.h> should be sorted alphabetically
- gtest macro should follow convention of ASSERT_EQ(expected, actual)
- removed unused variables: num, ecount_buf and kNotSecure
- TestQueryKeyStatus needs to call closeSession()
- moved and renamed test dependent global constants:
   e.g. k256SubSampleByteCount, k512SubSampleClearBytes and k512SubSampleEncryptedBytes
- use isOK() for checking Status::OK, e.g.
   ASSERT_TRUE(cryptoPlugin->setMediaDrmSession(sessionId).isOk());

Test: VTS test
  adb shell /data/nativetest/VtsHalDrmV1_0TargetTest/VtsHalDrmV1_0TargetTest

bug: 68735305
Change-Id: Ic8f43b4c35644bf7223f24a531eae818e59e0f4a