Background image upload: Fix issue showing uploaded images while saving is in progress

[itsmeichigo]

Closes: #15093

Description

This PR fixes the issue when uploaded images are not displayed when background image saving is in progress.

The solution:

• Enable reusing the action handler even when there are no pending uploads.
• Persist the product saved in the background and use it to determine hasUnsavedChangesOnImages.
• Remove product from active uploads when all images are done uploading. This is to make the logic simpler.

Steps to reproduce

1. Create or open an existing product with no images.
2. Select a few images to upload, save the changes and navigate back to the product list.
3. Wait a bit for the upload to complete but before the saving is done (notice the loading indicator is removed but the cover photo is not updated yet).
4. Open the product form and notice that the image list is filled with the uploaded images.
5. Navigate back and confirm that you're not asked to save any changes (neither when background saving is done or not).
6. Repeat the steps 1-4. Remove the new images and tap Save. Confirm that everything works correctly - the Save button is hidden after saving is done.

Testing information

Tested on simulator iPhone 16 Pro iOS 18.2 and confirmed that:

• Reopening product before background image saving is done shows uploaded images correctly.
• Background image saving handles the saving automatically.
• Saving the product after background image saving works correctly.
• No regression for loading animation on products with pending uploads.

Screenshots

Simulator.Screen.Recording.-.iPhone.16.Pro.-.2025-02-11.at.17.11.41.mp4

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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.

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• Ensure Adequate Unit Test Coverage: The changes are reasonably covered by unit tests or an explanation is provided in the PR description.
• Manual Testing: The author listed all the tests they ran, including smoke tests when needed (e.g., for refactorings). The reviewer confirmed that the PR works as expected on all devices (phone/tablet) and no regressions are added.

[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	pr15107-5b269e1
	Version	21.7
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	5b269e1
	App Center Build	WooCommerce - Prototype Builds #12952

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[itsmeichigo]

Attempt an additional fix for the reuse issue mentioned in #15052.

[pmusolino]

This seems to have fixed the issue, I'm not able to replicate it anymore! 👏

[pmusolino]

Everything works as expected 👏