Add Taiwan country code to be formatted for local calls to remove the

international prefix.

This change will also include a small refactor to store the country
codes in an array so other countries can be more easily added/removed.

Flag: com.android.internal.telephony.flags.national_country_code_formatting_for_local_calls

Bug: 293993310
Test: manual validity test, atest PhoneNumberUtilsTest
Change-Id: I0dfd133904103ff645a2d2ecb08c69a2cc9ede28