Encrypt keys even when device locked

Use ECDH public-key encryption to encrypt unlockedDeviceRequired keys
even when the device is locked.

Bug: 163866361
Test: keystore2_test
Test: atest android.keystore.cts.CipherTest#testEmptyPlaintextEncryptsAndDecryptsWhenUnlockedRequired
Change-Id: Idbb3e02972aba021d97c5284c300d3b5e97756ae
5 files changed