Add carrier-privileged app bypass for start/stopTethering

Allow carrier-privileged apps to call startTethering and stopTethering
for wifi tethering with a non-null SoftApConfiguration.

Bug: 295979433
Test: atest TetheringTests CtsTetheringTests

Change-Id: I7fae1964c44902b1d500729794fc59e5bdd185e5
6 files changed