docs: Adding update for DevicePolicyManager.getStorageEncryptionStatus()

and Direct Boot for DP5

getStorageEncryptionStatus() now returns new
ENCRYPTION_STATUS_ACTIVE_PER_USER if the device is not
using direct boot (and the not-new ENCRYPTION_STATUS_ACTIVE
is returned if direct boot is used)

Bug: 30112425
Change-Id: I27c11b2afe2afd9a19c9f8268f486b09af22e6ac