Freeze netd AIDL interface

This freezes the interface as of the latest beta build, although it has
not changed since then.

Generated with:
m netd_aidl_interface-freeze-api

Test: flashed, WiFi working
Test: atest netd_unit_test netd_integration_test netdutils_test
Bug: 128803828
Change-Id: Id1111242ca83c357d007959df830dbda4359216e