Enable outgoing emergency calls in LockTask mode.

As part of the LockTask 2.0 work, we allow DPCs to enable the system lock
screen in LockTask mode. When the device is protected by a PIN, pattern, or
password, the lock screen will have an entry point to the emergency dialer
which allows the user to make emergency calls (e.g., 911).

Therefore, we whitelist the activities that are necessary to place this
outgoing emergency call when LOCK_TASK_FEATURE_KEYGUARD is enabled.

Bug: 68750910
Test: bit FrameworksServicesTests:com.android.server.am.LockTaskControllerTest
Test: CTS verifier > CTS verifier > Managed provisioning > Device owner tests
      > LockTask UI
Change-Id: Iaeeec2c462b978d2d201c5660024a3dd7283ae07