PhoneNumberValidityChangeListener not called when navigate back

When navigate to another Fragment and then go back to phone Country Code selector fragment, not working phone formatter and phoneNumberValidatorChangeListener aren't call ever.

Set both on onViewCreated method:

```
layoutMobileFields.etPhoneCountryCode.setPhoneNumberValidityChangeListener
layoutMobileFields.etPhoneCountryCode.registerCarrierNumberEditText(layoutMobileFields.etPhoneNumber as EditText)
```

從 Fragment 的 onViewCreated 方法以及 issue 中所示的兩個 listener 和 registration 呼叫開始。重現離開並返回手機國碼選擇器的導覽流程，然後確認返回後電話格式化和 phoneNumberValidityChangeListener 回呼能夠正常運作。

由索引模型根據 Issue 內容生成。