Add privileged API to control keyguard secure notifications

I688e87cf09ad206f4f517a7be960c2aa01af8fc4, restricted privileged apps from silently becoming Device Admins.

Ia4e1ce9b81756e7f84ed0aa22d97e0b968cd8d89 added privileged APIs for locking the device and resetting the password.
We continue that work by providing an alternative for DevicePolicyManager#setKeyguardDisabledFeatures guarded by android.permission.CONTROL_KEYGUARD_SECURE_NOTIFICATIONS

Bug: 111153365
Bug: 112601004
Test: Secure notifications can be redacted on keyguard
Change-Id: If81cecf6e74f7abcff581a122c4b68cc04ff57c6