When an OTA is downloaded, the RecoverySystem can be triggered to store
the user's lock screen knowledge factor in a secure way using the
IRebootEscrow HAL. This will allow the credential encrypted (CE)
storage, keymaster credentials, and possibly others to be unlocked when
the device reboots after an OTA.
Bug: 63928581
Test: make
Test: boot emulator with default implementation
Test: boot Pixel 4 with default implementation
Change-Id: I1f02e7a502478715fd642049da01eb0c01d112f6
