Code changes:
 - Improve parsing logic to be smarter about national-prefix detection &
   stripping based on possible-lengths (IS_POSSIBLE_LOCAL_ONLY and
   INVALID_LENGTH). Enables e.g. adding Iran short-codes starting with "096"
   without the need to hack IR's national prefix parsing config.
 - Logging changes: Don't log client-provided phone numbers.
 - Add constants for C++ PhoneNumberUtil enums' max values.