wifi: refine API: notifyCountryCodeChanged

Feedback from API council:
1. Change to return void
2. Rethrow exception instead of logging
3. Consider passing and notifying the new value for country code

Bug: 216637965
Test: atest -c WifiNl80211ManagerTest
Trst: atest -c FrameworksWifiTests
Change-Id: If40f9434e20fd960a65de37c341d8bd6f57ed9d9
3 files changed