Follow up to #1551. Using `Codable.encodeAndDecode` we ensure that each value can be bidirectionally converted.
These tests exposed that unknown values were being encoded as `null`, but then failed to decode.

I've updated the implementation and added a few more tests to cover this behavior.

Follow up to #1551. Using `Codable.encodeAndDecode` we ensure that each value can be bidirectionally converted.
These tests exposed that unknown values were being encoded as `null`, but then failed to decode.

I've updated the implementation and added a few more tests to cover this behavior.

### Depends on:
- #1537
- #1540
- #1541
- #1543
- #1546
- #1547
- #1550
- #1551,
- #1565

### Changes

- Removed all custom deserialization code thanks to #1537, #1541, and #1543.
- The format of the customer info response is now very concise and only in one place (`CustomerInfoResponse`) instead of being passed through dictionaries and magic strings everywhere.
- `CustomerInfo` was combining the dictionaries inside of `"subscriptions"` and `"non_subscriptions"`, despite them having different formats. This is now made explicit through type conversions between the two, (see `CustomerInfoResponse.allTransactionsByProductId`).
- Removed all custom `CustomerInfo` errors since deserialization is automatic, and the underlying `Error` information will be provided thanks to `ErrorUtils.logDecodingError`.
- `CustomerInfo` deserialization always wraps errors into `ErrorCode.customerInfoError`, which is now also covered in a new test.
- Added a new snapshot test that covers `CustomerInfo` serialization by storing the result in a JSON file.

### Other changes:
- `CustomerInfo` equality is now automatic through the `CustomerInfoResponse` `Equatable` conformance.
- Simplified `schemaVersion` handling
- All tests still use `CustomerInfo(data: [String: Any])`, but that method is only visible for tests now, and it uses the underlying `Decodable` implementation (see `CustomerInfo+TestExtensions.swift`).
- Added extra tests for `CustomerInfoResponse` that use a fixture `CustomerInfo.json`, which is easier to maintain than having JSON in code.
- `RawDataContainer` implementation is changed in #1565.

### TODO:
- [x] Fix all tests
- [x] Update `RawValueContainer`
- [x] Consider recovering `CustomerInfoError`
- [x] Look at all previously logged errors
- [x] Finish `CustomerInfoResponseTests`
- [x] Handle all TODOs
- [x] Make `RawDataContainer` actually store all the original data: #1565