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: If9be53204a6e67edf7a68f74bd802848a3b86e26