WVCryptoPlugin was not properly implementing part of its responsibilities to
AES-CTR in ISO-CENC. Specifically, it was not incrementing the IV after each
block.
Also, I have greatly expanded the unit tests for decrypt() to catch more edge
cases.
This change fixes the two failing test vectors in the Java integration tests.
Copied from https://widevine-internal-review.googlesource.com/#/c/5123/2
Bug: 8656421
Change-Id: If935edbf01068f5b0d5254b4e657057ef57d8fcf
088288cb76