Store user's serial number in recoverable key store database.

Wipe data for deleted user on restart from
 * The database
 * Android KeyStore
 * Snapshot cache
Note that userId cannot be reused for different user at runtime and serial number is never reused.

Bug: 126241986
Test: atest FrameworksServicesTests:com.android.server.locksettings.recoverablekeystore
Change-Id: I91cd9e1baccd425a8a234b3da3d583f0920d4804