Add support for v2 policies to set_policy
Add support for v2 policies to set_policy

Extend the set_policy command to support setting v2 encryption policies,
in addition to v1 encryption policies which it currently supports.  This
uses the same ioctl FS_IOC_SET_ENCRYPTION_POLICY, where the 'version'
field at the beginning of the struct is used to determine whether the
struct is fscrypt_policy_v1 or fscrypt_policy_v2.

The command sets a v2 policy when the user gives the longer key
specification used in such policies (a 32 hex-char master_key_identifier
rather than a 16 hex-char master_key_descriptor).

Also add support for specifying the DIRECT_KEY, IV_INO_LBLK_64, and
IV_INO_LBLK_32 flags in the policy.  These are mostly for v2 policies,
though DIRECT_KEY can technically be used with v1 too.

google/fscryptctl,google/fscryptctl