Add support for testing mode root certificate.

1) Add Certificate
2) Helper class for end-to-end tests
3) Only create snapshot for passwords with special prefix in test mode
4) Sync only keys with insecure prefix in test mode.

Bug: 76433465
Test: adb shell am instrument -w -e package
com.android.server.locksettings.recoverablekeystore
com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner

Change-Id: I6edc8c4716c3a034b6b79c7aa6f4b8478e9a3c9e