[Woo POS] Variation pagination

[joshheald]

Part of: #14696

Description

This PR adds pagination support for variations in POS.

The feature works fully, but I think we can iterate on it a little in a future PR. There's a lot of duplication between the initial sync and next page sync – from a quick experiment, we could remove the initial sync and rely on defaults, especially since there's a separate resync function for PTR.

Steps to reproduce

Open the POS, and select a variable product to open.
Note that the first page is loaded, and if you have enough variations, scrolling down will load subsequent pages until all variations are loaded.

Testing information

N.B. The page size is still 100 in this PR; in #14843 it will be reduced to 25.

For testing, I recommend reducing it to 15 so you can see more pages loaded. If you choose too small a number that doesn't fill the screen, the scroll observation to trigger next page load won't work.

Additionally, variations will only show up if you're using WC 9.6, which is not yet released. You can work around this by commenting out ProductsRemote line 214, so that the root products list is not filtered to simple products only.

//            ParameterKey.productType: POSConstants.productType,

Screenshots

variation.pagination.mp4

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[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	pr14849-3b33919
	Version	21.4
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	3b33919
	App Center Build	WooCommerce - Prototype Builds #12498

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[jaclync]

Works great! I noticed an infinite scroll issue from the trigger state which I will fix separately.

The feature works fully, but I think we can iterate on it a little in a future PR. There's a lot of duplication between the initial sync and next page sync – from a quick experiment, we could remove the initial sync and rely on defaults, especially since there's a separate resync function for PTR.

I agree, the initial load could just use the PTR resync IMO. The difference between initial load and reload seems to be just resetting the internal states in the reload, which works for the initial load as well. I will try including this in the PTR work next.

[jaclync]

nit: we can remove this TODO comment now

[jaclync]

Update: removed in 3b33919.