[Forwardport] Fix type error in Cart/Totals.

[nmalevanec]

Description

Original pull request: magento-engcom/magento2ce#1186
Unset the address extension attributes before trying to create the quote totals.

Fixed Issues (if relevant)

1. Type error in Cart/Totals #12993: Type error in Cart/Totals
2. CartTotalRepository cannot handle extension attributes in quote addresses in 2.2.2 #12819: CartTotalRepository cannot handle extension attributes in quote addresses in 2.2.2

Manual testing scenarios

1. Define extension attributes for the quote billing address
2. Login as a user who has at least two addresses in his address book
3. Add a virtual product to card and proceed to checkout
4. Choose or change the billing address, click update, note no errors.

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-engcom-team]

Hi @nmalevanec. Thank you for your contribution
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[fooman]

The original PR is unfortunately not public. I am however concerned that the proposed solution here essentially simply deletes data.

[fooman]

@antonkril a while ago we talked about issues around extension attributes. This is an example where I believe a better solution needs to be found.

The need to unset them, to me indicates, there is some gap with Extension Attributes in general which should be addressed on a higher level than fixing random occurrences of error messages with an unset.

[magento-engcom-team]

Hi @nmalevanec. Thank you for your contribution.
We will aim to release these changes as part of 2.3.0.
Please check the release notes for final confirmation.