set the country code when initializing the ot-daemon The country code is lost after the ot-daemon is restarted. This CL stores the country code to persistent settings and reads out the previously stored country code to set the country code when the ot-daemon is initialized. Bug: b/326021472 Test: atest ThreadNetworkUnitTests Change-Id: I6982a57ba4845f5a45f3366400c531398e82339e