Increase the master key size to 256 bits

NIAP certification finds that the 128 bit key size is insufficient
and requires a 256 bit key size. This change increases the
size of new master keys to 256 bits. Any existing master keys are
not changed and continue to be supported.

A new BlobType, TYPE_MASTER_KEY_AES256, is used to signal when a
key is the new larger size.

Bug: 121272336
Test: (1) Ran Keystore CTS tests against Walleye.
      (2) Created keys in build without change, moved to build
          with change and verified old key could be loaded and
	  used. Also, a new key could be created with the
	  increased size and could be reloaded after a reboot.
Change-Id: If00331c303e6cc7bc95a2ab624d0e19bec4e587e
4 files changed