DO NOT MERGE Add network logging icon to Quicksettings when enabled

Add the network logging icon in Quick Settings' footer if
network logging is enabled, possible next to the VPN icon.
Quicksettings has to be able to tell that network logging
is enabled, so this CL changes DPM.isNetworkLoggingEnabled() to be
callable from the device owner or from any app with the MANAGE_USERS
permission.

The icon is only a placeholder until the official icon is finished.

CTS Verifier tests will be added when all Network logging UX changes are
done.

Cherry-picked from master, and then modified to work in N:
I had to remove the QSFooterTest change because the testing infrastructure
is not there in N. Also, I had to add DPMS.enforceDeviceOwnerOrManageUsers()
to which did not exist in N before.

BUG: 33126618
BUG: 29748723
Test: Manual, CTS-Verifier tests will be added in a follow-up

(cherry picked from commit a4e169ed)

Change-Id: Ib35d323605ab11f883a4b6199d1db79b9e53c49b