Change system API getDeviceId to be @NonNull

This is to address the feedback from api council that
OpEventProxyInfo#getDeviceId should be @NonNull. The device Id will be
set to VirtualDeviceManager.PERSISTENT_DEVICE_ID_DEFAULT when the
parameter passed to the constructor is null.

Flag: android.permission.flags.device_id_in_op_proxy_info_enabled
Test: presubmit
Bug: 341319360
Change-Id: I95ade50744ec80fc24a559547bc0bb8e2c17373c