[Backport] Bug fix for #21753 (2.2-develop)

[crankycyclops]

Description (*)

Fixes the issue raised in #21753 by setting the initial downloadable item status to Available if \Magento\Downloadable\Model\Link\Purchased\Item::XML_PATH_ORDER_ITEM_STATUS is set to 'Pending.'

Fixed Issues (if relevant)

1. Order Item Status to Enable Downloads is set to "Pending," but no download links are presented in "My Downloads" when logged in (fix provided) #21753

Manual testing scenarios (*)

1. Login to the admin and set Stores -> Configuration -> Catalog -> Downloadable Product Options -> Order Item Status to Enable Downloads to "Pending"
2. Create a downloadable product in the admin
3. Create a user account on the frontend and login
4. Purchase a downloadable product. The product should be placed in the "available" state after successful completion of payment.
5. Login to the admin and set Stores -> Configuration -> Catalog -> Downloadable Product Options -> Order Item Status to Enable Downloads to "Invoiced"
6. Purchase the product again and note the second ordered item is in the "pending" status.

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)
  Backport for: Bug fix for #21753 (2.3-develop) #22073

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[rogyar]

I'm putting this PR on hold until another version for 2.3 is merged

[crankycyclops]

@rogyar, just letting you know when you're ready to merge that I've made the same changes to this branch that were requested in the PR for 2.3.

[magento-engcom-team]

Hi @orlangur, thank you for the review.
ENGCOM-4777 has been created to process this Pull Request

[VasylShvorak]

✔️ QA passed

[m2-assistant]

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