Add the ability to configure NTP port for tests

Add the ability to configure NTP port for tests via the command line and
the associated plumbing / knock-ons.

In-progress CTS tests will run a fake NTP server on the device itself.
Binding to NTP's default port of 123 is restricted. Therefore, we need
to be able to override the port for tests.

adb shell cmd network_time_update_service set_server_config --port 9999
adb shell dumpsys network_time_update_service
<observe port value>
adb shell cmd network_time_update_service force_refresh
<observe false>

adb shell cmd network_time_update_service set_server_config
adb shell dumpsys network_time_update_service
<observe port value>
adb shell cmd network_time_update_service force_refresh
<observe true>

Bug: 213393821
Test: See above
Change-Id: I21e8b735fab268df0d617848b8a562f86560ad16