Manual implementation of PartialEq for Code

[rubdos]

Fix #55 and #28

We go from 16 failed round-trip parsing cases to 4.

Previous:

    phone_number::test::round_trip_parsing::case_02::mode_4
    phone_number::test::round_trip_parsing::case_03::mode_4
    phone_number::test::round_trip_parsing::case_04::mode_4
    phone_number::test::round_trip_parsing::case_05::mode_4
    phone_number::test::round_trip_parsing::case_06::mode_4
    phone_number::test::round_trip_parsing::case_07::mode_4
    phone_number::test::round_trip_parsing::case_08::mode_1
    phone_number::test::round_trip_parsing::case_08::mode_4
    phone_number::test::round_trip_parsing::case_09::mode_1
    phone_number::test::round_trip_parsing::case_09::mode_4
    phone_number::test::round_trip_parsing::case_10::mode_1
    phone_number::test::round_trip_parsing::case_10::mode_4
    phone_number::test::round_trip_parsing::case_11::mode_1
    phone_number::test::round_trip_parsing::case_11::mode_4

Current (only cases pertaining to #46 still remain!):

---- phone_number::test::round_trip_parsing::case_10::mode_1 stdout ----
-------------- TEST START --------------
Error: parsing +15208782491 with country hint None after formatting in International mode as +1 520-878-2491

Caused by:
    invalid country code

---- phone_number::test::round_trip_parsing::case_08::mode_1 stdout ----
-------------- TEST START --------------
Error: parsing +13459492311 with country hint None after formatting in International mode as +1 345-949-2311

Caused by:
    invalid country code

---- phone_number::test::round_trip_parsing::case_11::mode_1 stdout ----
-------------- TEST START --------------
Error: parsing +15208782491 with country hint None after formatting in International mode as +1 520-878-2491

Caused by:
    invalid country code

---- phone_number::test::round_trip_parsing::case_09::mode_1 stdout ----
-------------- TEST START --------------
Error: parsing +16137827274 with country hint None after formatting in International mode as +1 613-782-7274

Caused by:
    invalid country code


failures:
    phone_number::test::round_trip_parsing::case_08::mode_1
    phone_number::test::round_trip_parsing::case_09::mode_1
    phone_number::test::round_trip_parsing::case_10::mode_1
    phone_number::test::round_trip_parsing::case_11::mode_1

This breaks public API, so this is 0.4 material. I have some things up queue for one more 0.3 release, so let's wait a bit to merge this.

[gferon]

Converting to draft so I don't merge it by accident 😅