Add MANAGE_SAFETY_CENTER permission.

Only for use by SafetyCenter (PermissionController), and shell for CTS
tests.

Test: atest CtsSafetyCenterTestCases
Bug: 203205376
Ignore-AOSP-First: Not announced yet, and permission hasn't been merged
in AOSP

Change-Id: I0f2ac01a0fc340b48d30b3e2006c2726a88c52a9