Add config value and a new permission for SafetyCenter.

Also giving it to the Shell for Cts purposes.

Test: atest CtsSafetyCenterTestCases
Bug: 208421513

Ignore-AOSP-First: Not announced yet, and need to use a permission
that hasn't been merged in AOSP

Change-Id: I2c63c54efac0add7c412fa43b77fa18ba2e486c3