[Local catalog] Prevent duplicated attributes in variation names

[joshheald]

Description

This PR prevents variations from getting duplicated attributes in their names.

Previously, if a variable product was edited, its attributes would be added to the database again on the next incremental sync. This resulted in its variation's names showing the same components multiple times, making it harder to fit and identify a variation by name.

Cause

Attributes were duplicated in the database because although we use save, which upserts items, they wouldn't update, because they use an auto-incremented primary key. This is due to "local attributes" all having an ID of 0 (local to the product, not related to local catalog.)

GRDB identified the attributes as new, and inserted them instead, which meant that the calculation of the variation's name pulled in all the copies of the attribuet.

Fix

To fix this, we simply delete all attributes for updated products before inserting them again during incremental syncs. The catalog always includes all attributes, even if they're unchanged, so this is safe (unlike with variations.)

Test Steps

1. Open POS and perform a full sync in settings
2. Edit a variable parent product in wp-admin (it doesn't matter what you edit)
3. Pull to refresh to force an incremental sync
4. Exit POS and open it again
5. Open the variable product
6. Observe that all the attributes used for the variation names are not duplicated

N.B. I noticed that changes to attributes don't trigger observation updates for variation names which should change, which is why you need to exit and reopen POS to see the changes. I'll fix that separately.

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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.

[wpmobilebot]

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

	App Name	WooCommerce iOS Prototype
	Build Number	pr16399-b357920
	Version	23.7
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	b357920
	Installation URL	0ud8ud0mta2eo

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[iamgabrielma]

Good catch, worth adding this to the test plan if it hasn't yet, might uncover some other little details when testing in different stores

LGTM! 🚢