[Order Details] Fix race condition for missing products request

[ealeksandrov]

Closes: #7132

Description

This PR fixes race condition in Order Details screen, so products are always correctly loaded and displayed in edit flow.
Also it prevents some empty products sync requests when no data update is needed.

How

The method syncEverything in OrderDetailsViewModel have separate syncOrder() and syncProducts() calls which are run in parallel.
In fact, products sync depends on order, because simple order (from the list, non-cached previously) doesn't have items data with product ids to sync at all. This is an edge case, because usually products and/or order are already cached.

Testing

1. Logout, log back in to clear cache.
2. Go to Orders List.
3. Open Order Details.
4. Confirm products list with thumbnails is loaded (if products sync failed, list will also be there, but with basic data, no thumbnails)
5. Tap "•••" in navbar. Select "Edit".
6. Confirm products list is displayed correctly on Order Edit screen.

Screenshots

before	after

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-woocommerce]

	Warnings
⚠️	This PR is assigned to a milestone which is closing in less than 4 days Please, make sure to get it merged by then or assign it to a later expiring milestone

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[Ecarrion]

Works great! Thanks for fixing this @ealeksandrov!