Fix/authenticator/phone validator

[ekjotmultani]

Issue #, if available: #4079

Description of changes:

• Drop the country code prefix before performing validation
  This is done in the exact same way as this rolled back fix from November last year. This fix was correct for the main issue in the original issue however it didn't address being able to re-input a dial code and still have it pass through validation

• Truncate a re-inputted dial code if it exceeds the maximum length of a phone number from that given country
  Using a map of dial codes to their countries' maximum length of phone number (generated from https://github.com/google/libphonenumber/tree/master), we will check if the inputted phone number begins with the selected dial code, if it does, then check if it surpasses the length of number in that country (since it could be the case that the number naturally begins with the dial code), if this is also true then ignore the repeat dial code and take the leftover number as the phone number

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