AndroidKeyStore: Add encrypted flag

Add the encrypted flag for the KeyPairGenerator and the KeyStore so that
applications can choose to allow entries when there is no lockscreen.

(partial cherry pick from commit 2eeda7286f3c7cb79f7eb71ae6464cad213d12a3)

Bug: 8122243
Change-Id: I5ecd9251ec79ec53a3b68c0fff8dfba10873e36e
9 files changed