CTS tests for entropy consumption by Cipher and Signature.

This adds CTS tests that assert that the correct amount of entropy
is consumed by Android Keystore's Cipher encrypt/decrypt operations
and Signature signing operation.

Unfortunately, due to Bug 22485587 the entropy test for Signature
primitive is disabled.

Bug: 21936191
Change-Id: I356abc4f5e0996d7fc555f95d8a0ec02f475eb96
3 files changed