(This change is merged from http://go/wvgerrit/124825)
The OEMCrypto tests have tests that verify that entitled keys can be
loaded but not that they can be successfully used for decrypt. This
patch adds a decrypt portion to the existing tests.
As part of this, the existing Session::EncryptCTR() method and portions
of Session::TestDecryptCTR() are lifted to be static functions so they
can be shared across unrelated classes in oec_session_util.cpp.
EncryptCTR() had no dependence on its enclosing class and is unchanged
other than being moved outside the class.
To reduce ambiguity with the new decrypt verification, this patch also
renames EntitledMessage::VerifyEntitlementTestKeys() to the
more-specific EntitledMessage::VerifyKCBs(). Its behavior is unchanged.
Bug: 186782279
Test: x86-64 platform
Test: opk_ta platform
Test: build_and_run_all_unit_tests
Change-Id: I15156882907b0987215087aaf43b4666fedc171a
d742daf9c7