[Tablet Orders] Make order sync blocking in side-by-side mode to improve product selection sync reliability

[joshheald]

Part of: #11908

Description

This isn't pretty.

With the side-by-side order creation process, we sync product selections and removals as soon as they are performed.

This makes it easy to rapidly make significant changes to the order, which is not reliable. In particular, by quickly selecting and deselecting multiple products, it's easy to get the product selector out of sync with the order.

This PR implements the simplest fix, which is to always block the UI when a change is in flight. We only block when the side-by-side mode is used.

Unfortunately, this currently includes quantity changes, which makes that part of order creation frustrating to use.

This PR may be OK for a temporary solution, or it may be better to allow the potential out-of-sync orders... but neither are good.

Testing instructions

1. Enable the sideBySideViewForOrderForm feature flag
2. Launch the app on an iPad, and go to the Orders tab. Tap +
3. Add a product to the order – observe that the UI is blocked while the sync completes
4. Add another – observe that it's blocked again
5. Remove a product – observe that the UI is blocked
6. Open a product card and change the quantity – observe that you get a moment to tap it multiple times, if you're fast, but then the UI is blocked for the sync.
7. Set a split view so that the screen shows in modal-on-modal
8. Change a product's quantity – observe that the UI is not blocked.

Screenshots

https://github.com/woocommerce/woocommerce-ios/assets/2472348/b0735067-f7e7-4a3b-945a-647173e91754

---

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

[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce iOS by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce iOS
	Build Number	pr12055-7a533ef
	Version	17.4
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	7a533ef13c80ed019ca5fe74cbcce2bdbb9eceef
	App Center Build	WooCommerce - Prototype Builds #8113

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[dangermattic]

	1 Warning
:warning:	This PR is assigned to the milestone 17.5. This milestone is due in less than 2 days. Please make sure to get it merged by then or assign it to a milestone with a later deadline.

Generated by :no_entry_sign: Danger